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FOREST PHYSIOGRAPHY 

PHYSIOGRAPHY OP^ THE UNITED STATES 

AND PRINCIPLES OF SOILS IN 

RELATION TO FORESTRY 



BY 

ISAIAH BOWMAN, Ph. D. 

Assistant Professor of Geography in Yale University 



FIRST EDITION 

FIRST THOUSAND 



NEW YORK 

JOHN WILEY & SONS 

London: CHAPMAN & HALL, Limited 

1911 






\ 



Copyright, 191 i 

BY 

ISAIAH BOWMAN 



i-> 



Stanbopc ipresa 

F. H. GILSON COMPANY 
BOSTON, U.S.A. 



©CI.A297922 



To 

LEADER IN AGROGEOLOGY 



PREFACE 



Students of forestry in the United States are constantly demandng 
a guide to the topography, drainage, soils, and climatic features of the 
country. The need for such a book is keenly felt, since students in the 
professional schools of forestry have little time for the study of origins 1 
sources of material in a subject which is not forestry but the basis of 
forestry. On the other hand, such general sources as are available are 
both too brief and too elementary for the somewhat comprehensive 
requirements of the American forester. 

In preparing this book I have attempted to steer a middle course be- 
tween that purely descriptive writing with which the forester is too 
often satisfied, and that altogether explanatory writing which the techni- 
cal physiographer is inclined to regard as the real substance of a scientific 
book. The descriptive portions are intentionally rather comprehensive, 
for the relief and not the explanation of it is of immediate value to the 
forester, no matter how important the explanation may be in assisting 
him to appreciate and remember the relief. A chief concern has been 
the reduction of geologic data to a minimum. A geologic statement 
frequently runs off into so many consequences that the most important 
of these almost force one to a more extended and complex discussion than 
the forester, a lay student of geologic and geographic science, can assimi- 
late. Emphatically, some geologic data are essential, but only in so far 
as they have an immediate physiographic bearing. 

A further point concerning the organization of the material of this 
book requires statement here. It seems so clear that one can not know 
forestry without knowing under what physical conditions trees grow, 
that one finds it impossible to see how even the least philosophical view 
of the subject can exclude a knowledge of physiography. It would 
seem that one should pay a great deal of attention to lumbering as re- 
lated to drainage and relief, to silviculture as related to soils, climate, 
and water supply, and in general that one should emphasize the forester's 
dependence upon physical conditions. This would appear to be so plain 
a doctrine as not to require restatement here, were it not for the fact 
that some students of forestry and even some schools of forestry still 



Vlll PREFACE 

pay too little attention to the subject. If the forest is accepted merely 
as a fact, and the chief concern is its immediate and thoughtless exploita- 
tion, physiography may indeed be the fifth wheel to the coach, although 
even so practical a view as the lumberman's must include some knowl- 
edge of tonography and drainage if merely to put forest products upon 
the m? CvCt. But forestry is more than lumbering, and if forests are to 
be r nserved, if they are to be improved and extended, every direct rela- 
tion of the tree to its physiographic environment is vital. 

The title, "Forest Physiography," does not imply a book on forestry 
but rather a book on physiography for students of forestry; and, as 
nearly as has seemed advisable from the nature of the subject, it has 
been prepared for their special needs. It is hoped, however, that the 
book may be of service to historians also, and to economists, since a 
knowledge of the physiography of the United States has heretofore 
depended upon one or two short and general chapters on the subject, or 
upon a study of hundreds of original papers and monographs. 

No attempt has been made to show the connection between soils and 
agriculture, which is the general theme of text-books on soils. Neither 
has it been attempted to make a comiplete classification of all the types 
of rocks and soils found in nature. The distinctions which such a classi- 
fication implies may be serviceable to the geologist, the farmer, and the 
gardener, but they are too finely drawn for the forester, whose needs are 
met by a broader classification based upon qualities of wider application. 
It is our purpose to discuss the origin of soil, and the physical and chemi- 
cal transformations it undergoes in the process of gradual decay and of 
interaction with the plants that thrive upon it. Soil water, drainage, 
plant foods in the soil, soil warmth, and soil improvement are additional 
topics; the most important point of all concerns the actual preserva- 
tion of soils that occur upon forested lands. In a broad way all soils 
are an inheritance from a geologic past; they are slow of accumulation, 
precious, and vital to man's welfare, for agriculture is the basis of our 
modern organized life, and soil is the basis of agriculture. Imprudent 
forest cutting and thoughtless land tillage tend to disturb a natural 
balance between great forces. That they may be a sowing to the wind 
is amply shown by the whirlwind of destruction which man is reaping 
in extensive tracts of deforested, soilless uplands of America, Europe, 
and Asia. Forestry affects not only trees but also soils, one of the 
greatest of man's geologic inheritances. 

I am under obligations to many for advice and assistance. First of 
all to Prof. H. E. Gregory, who has given most generously of his time in 
reading both manuscript and proof. Prof. J. Barrell gave helpful advice 



PREFACE IX 

in the preparation of certain chapters in Part One, and Prof. J. W. 
Tourney of the Yale Forest School supplied important criticisms. Dr. 
G. E. Nichols of the Sheffield Scientific School made a large number of 
corrections and alterations in the botanical descriptions. Prof. E. W. 
Hilgard of the University of California, and his colleague. Prof. R. H. 
Loughridge, have read Part One with great care, and the benefit of their 
searching criticisms lays me under deep obligations. My obligations to 
Professor Hilgard extend beyond this, however, for his great work on 
soils has been an invaluable source of experimental data. 

The United States Geological Survey has followed its usual generous 
policy and suppHed many of the illustrations. Prof. R. DeC. Ward has 
kindly allowed me to use the expensive original drawings of two climatic 
maps after Koppen. A number of publishers, acknowledged in a sepa- 
rate list, have permitted the reproduction of illustrative material. I 
have also obtained illustrations from the Canadian Geological Survey, 
Prof. C. R. Gould of Oklahoma University, Prof. C. A. Reeds of Bryn 
Mawr, Mr. H. Brigham, Jr., of Cortez, Colorado, and a number of my 
students in forest physiography. 

ISAIAH BOWMAN. 

Yale University, 
June lo, 191 1. 



ACKNOWLEDGMENT OF ILLUSTRATIONS 



Fig. lo, p. 91, from H. W. Wiley, Soils, Chemical Publishing Com- 
pany, Easton, Penn. 
Fig. II, p. 99, from E. W. Hilgard, Soils, Macmillan Company, N. Y. 
Fig. 13, p. Ill, and Fig. 14, p. 113, from R. DeC. Ward, Climate, 

G. P. Putnam's Sons, N. Y. Based on Koppen. 
Fig. 29, p. 146; Fig. 48, p. 1S9; Fig. 61, p. 230; Fig. 62, p. 231, 

from F. H. Newell, Irrigation in the United States. 
Fig. 80, p. 285, from Gilbert and Brigham, Physical Geography, 

D. Appleton & Co. 
Fig. 271, p. 676. From E. de Martonne, Traite de Geographie Physique, 

Armand Colin, Paris, France. 
The largest number of illustrations are from the Collections of the 

United States Geological Survey. 
A number of the block diagrams of the Basin Ranges are from W. M. 

Davis, Mountain Ranges of the Great Basin, Bull. Mus. Comp. 

Zool. 



CONTENTS 



PART ONE — THE SOIL 

Chapter Page 

I. The Importance, Origin, and Diversity of Soils i 

The Soil in Relation to Life , i 

The Soil and the Forest i 

The Maintenance of a Soil Cover 3 

Soil-making Forces 7 

The Causes of Soil Diversity 22 

II. Physical Features of Soils 27 

Size and Weight of Soil Particles 27 

Pore Space and Tilth 28 

Special Action of Clay 30 

Soil and Subsoil 30 

Soil Air 33 

Loam, Silt, and Clay 34 

III. Water Supply of Soils 41 

Relation to Plant Growth and Distribution 41 

Forms of Occurrence 44 

IV. Soil Temperature 55 

Ecologic Relations 55 

Influence of Water on Soil Temperature 56 

Soil Temperature and Chemical Action 57 

Influence of Slope Exposure, Soil Color, Rainfall, and Vegetation 58 

Temperature Variations with Depth 60 

V. Chemical Features of Soils 62 

Relative Value of Chemical Qualities 62 

Soil Minerals 63 

Elements of the Soil 64 

Relations of Soil Elements to Plants 65 

Characteristics and Functions of the Principal Soil Elements .... 66 

Total Plant Food; Available Plant Food 73 

Determination of Soil Fertility 74 

Harmful Organic Constituents of the Soil .• 76 

VI. Humus and the Nitrogen Supply of Soils 77 

Sources and Plant Relations 77 

Organic Matter in the Soil 79 

Soil Humus .- 80 

VII. Soils of Arid Regions 95 

General Qualities 95 

Alkali Soils 97 

VIII. Soil Classification 102 

Purpose of Soil Analysis 104 

Different Bases of Soil Classifications 105 



Xll CONTENTS 

PART TWO — PHYSIOGRAPHY OF THE UNITED STATES 

Chapter Page 

IX. Physiographic Regions, Climatic Regions, Forest Regions . . . 107 

Introduction '. 107 

Physiographic Regions 108 

Climatic Regions. iii 

Forest Regions 123 

X. Coast Ranges 127 

Subdivisions 127 

Coast Ranges of California 127 

The Klamath Mountains 138 

Coast Ranges of Oregon 142 

Olympic Mountains : 144 

Climate, Soil, and Forests 145 

XI. Cascade and Sierra Nevada Mountains 149 

Cascade Mountains .' 149 

Central Cascades 149 

Soil, Chmate, and Forests 162 

Sierra Nevada Mountains 166 

XII. Pacific Coast Valleys 177 

General Geography 177 

Willamette, Cowlitz, and Puget Sound Valleys 178 

Great Valley of Cahfornia 179 

Valley of Southern California 184 

Soils of the Pacific Coast Valleys 188 

XIII. Columbia Plateaus and Blue Mountains 192 

Columbia Plateaus 192 

E.xtent and Origin 192 

Buried Topography Beneath the Basalt 194 

Drainage Effects of the Basalt Floods 196 

Deformations of the Basalt Cover 198 

Coulees of the Columbia Plateaus 200 

Stream Terraces 201 

Climate, Soil, and Vegetation 202 

Blue Mountains 207 

XIV. Great Basin 210 

Arid Region Characteristics; Hydrographic Features 210 

Salt Lakes of the Great Basin 210 

Rivers of the Great Basin; Precipitation 216 

Special Topographic Features 217 

Basin Ranges 218 

Soils of the Great Basin 229 

Forests and Timber Lines 230 

XV. Lower Colorado Basin 236 

Types of Lowlands 237 

Salton Sink Region 240 

Climate, Soil, and Vegetation 243 

XVI. Arizona Highlands 246 

Topography and Drainage 246 

Soils and Vegetation 247 

Regional Illustrations 250 

Eastern Border Features 253 

Rainfall and Rings of Growth of Trees 254 



CONTENTS xiii 

Chapter Page 

XVII. Colorado Plateaus 256 

High Plateaus of Utah 260 

Grand Canyon District 268 

Southern Plateau District 273 

Grand River District 276 

Physiographic Development; Erosion Cycles 281 

Climatic Features and Vegetation 286 

Mountains of the Plateau Province 290 

XVIII. Rocky Mountains. 1 298 

Northern Rockies 298 

XIX. Rocky Mountains. II 329 

Central Rockies 329 

Extra-Marginal Ranges 345 

XX. Rocky Mountains. Ill 356 

Southern Rockies 356 

XXI. Trans-Pecos Highlands : 387 

Mountains and Basins 387 

Mountain Types 389 

Drainage Features 397 

Longitudinal Basins 398 

Climate, Soil, and Vegetation 401 

XXII. Great Plains 405 

Topography and Structure 405 

Stream Types 409 

Regional Illustrations 410 

Vegetation 425 

XXIII. Minor Plateaus, Mountain Groups, and Ranges of the Plains 

Country 43 1 

Edwards Plateau 431 

Black Hills 440 

Outlying Domes 444 

Little Belt, Highwood, and Little Rocky Mountains 445 

Ozark Province 451 

Arkansas Valley 455 

Ouachita Mountains 456 

Arbuckle Mountains 456 

Wichita Mountains 458 

XXIV. Prairie Plains 460 

Extent and Characteristics. . 460 

Glacial and Interglacial Periods 466 

Topographic Drainage and Soil Effects .-; 469 

Soils of the Glaciated Country 486 

Tree Growth of the Prairies 489 

Driftless Area 494 

XXV. Atlantic and Gulf Coastal Plain (Including the Lower 

Allitvial Valley of the Mississippi) 498 

General Features and Boundaries 498 

Fall Line 499 

Relation to the Continental Shelf 499 

Materials of the Coastal Plain 500 

Subdivisions 501 

Cape Cod-Long Island Section 502 



XIV CONTENTS 

Chapter Page 
XXV. Atlantic and Gulf Coastal Plain {Continued). 

New Jersey-Maryland Section 514 

Virginia-North Carolina Section . 518 

South Carolina- Georgia Section 519 

Alabama-Mississippi Section '. 520 

Mississippi Valley Section 524 

Louisiana-Texas Section 529 

Soils 539 

Tree Growth of the Coastal Plain 540 

XXVI. Peninsula of Florida 543 

General Geography 543 

Geologic Structure 545 

Physiographic Development 545 

Topography and Drainage 546 

Soils and Vegetation 552 

XXVII. Laurentian Plateau and its Outliers in the United States . . . 554 

Laurentian Plateau 554 

Superior Highlands 572 

Adirondack Mountains 578 

XXVIII. Appalachian System 585 

General Features, Subdivisions, and Categories of Form 585 

Physiographic Development 590 

Relation of Topography to Rock Types 596 

Glacial Effects 599 

XXIX. Older Appalachians 603 

Southern Appalachians and Piedmont Plateau 603 

Appalachian Mountains , 603 

Blue Ridge 619 

Piedmont Plateau 623 

XXX. Older Appalachians [Continued) 636 

Northern or New England Division 636 

Upland Plain of New England 637 

Geologic Features 638 

Effects of Glaciation 640 

Subregions of the New England Province. 645 

XXXI. Newer Appalachians 665 

Introductory 665 

Southern District 666 

Stream Types 668 

Central District 670 

Northern District 679 

Tree Growth 683 

XXXII. Appalachian Plateaus 685 

Northern District 685 

Central District, 694 

Southern District 695 



Local Lowlands. 



700 



XXXIII. Lowland of Central New York 707 

Finger Lakes 709 

Abandoned Channels yn 

Drumhn Types and Belts 716 



CONTENTS XV 

Appendix A: Page 

Soil Class; Soil Type; Soil Series 721 

Unclassified Materials; Special Designations 723 

Appendix B: 

Outline for a Soil Survey in Forest Physiography 726 

Appent)ix C: 

Analyses of Five Common Rock Types in Their Fresh and in Their Decom- 
posed Condition 728 

Analyses of Fresh and of Decomposed Gneiss, Albemarle Count}', Virginia. 728 
Analyses of Fresh and of Decomposed Diorite from Albemarle County, 

Virginia 729 

Analyses of Fresh and of Decomposed Argillite, Harford County, Maryland 729 

Analyses of Fresh Limestone and Its Residual Clay 729 

Appendix D: 

The Geologic Time Table 730 



LIST OF ILLUSTRATIONS 



Figure Page 

1. Effects of changing temperatures on rock masses 14 

2. Underground burrows and chambers of earthworm population in well- 

drained sand bank near New Haven 18 

3. Diagram to illustrate pore space in soils 28 

4. The most compact packing of a mass of spheres 28 

5. Ground water in relation to the surface and the bed rock 44 

6. Contour map of water table 45 

7. Capillary water and ground water 51 

8. Influence of surface slope upon the amount of heat received 58 

9. Nitrogen changes in the soil produced by the action of bacteria 89 

10. Nitrous ferment prepared from soil from Cito and nitric ferment from the 

same source 91 

11. Amouiits and composition of alkali salts 99 

12. Elutriator (Hilgard's) in position for soil analysis 103 

13. Koppen's classification of climates in relation to vegetation iii 

14. Temperature zones of the western hemisphere 113 

15. Normal surface temperatures for July 114 

16. Normal surface temperatures for January 115 

17. Average date of last killing frost in autumn 116 

18. Average date of first killing frost in spring 116 

19. Mean annual rainfall in the United States 118 

20. Absolute minimum temperatures 119 

21. The average annual humidity of the air in the United States 119 

22. Percentage of annual rainfall received in the six warmer months 120 

23. Forest regions of the United States 124 

24. Map of Cahfornia 129 

25. Coastal terraces produced by wave erosion, California 134 

26. Redlands and San Bernardino and San Gorgonio Peaks, California 136 

27. Bear Valley and the adjacent country, San Bernardino Range 137 

28. Boundaries between the Sierra Nevada, Cascades, Coast Ranges, and the 

Klamath Mountains 141 

29. Western forests and woodlands 146 

30. Profile across the Chelan Range (Cascades) 150 

31. Accordant ridge crests of the Cascades 151 

32. Details of Cascade topography 152 

2,2,. View of High Cascades from near Cascade Pass 153 

34. Relations of former and present forest near Prospect Peak, California 155 

35. Cathedral Peak, Okanogan Mountains, Washington 157 

36. Plateau of the Cascades 159 

37. Relief map of Mount Hood, Oregon. . ; 161 

38. Topographic profile in relation to rainfall in the Coast Ranges and the Cas- 

cades of Oregon 163 

39. Altitudinal range and development of timber-tree species in the central 

portion of the Cascade Mountains 164 

40. Typical portion of Yosemite Valley 

41. Relation of topography to rainfall, Sierra Nevada Mountains 

42. Ranges of four characteristic species in the northern Sierra Nevada 17 

43. Base-leveled plain on the northern border of the Great Valley of California 18^ 

44. Bench lands, coastal plains, and mountains of southern California 185 

45. Inner edge of the coastal plain of soutljern California 186 

46. West Riverside district, California .' 187 

xvii 




XVHl LIST OF ILLUSTRATIONS 

Figure Page 

47. West Riverside district, California. This view panoramic with Fig. 46 . . . 187 

48. Irrigation map of the West 189 

49. Lava fields of the Northwest 192 

50. Canyon of the Snake River at the Seven Devils 195 

51. South shore of Malheur Lake, Oregon '. 197 

52. Sketch map of southeastern Oregon 199 

53. Drainage basins of the Great Basin 211 

54. Post-Quaternary faults of the Great Basin 215 

55. Longitudinal profiles of a number of the Basin Ranges 219 

56. Plan of the principal faults in the Bullfrog district, Nevada 220 

57. Fault-block displacements in the Bullfrog district, Nevada 220 

58. Diagram of fault-block mountains of the Great Basin 223 

59. Post-Quaternary fault on the south shore of Humboldt Lake 226 

60. Ravines, spurs, and terminal facets of the Spanish Wasatch 227 

61. Location of vacant public land ' 230 

62. Approximate location and extent of open range in the West 231 

63. Typical view of desert vegetation 232 

64. East side of Snake Range, Nevada 234 

65. Part of Colorado Valley '. . . . 239 

66. Salton Sink region 242 

67. Geologic section from Colorado River to Colorado Plateaus 247 

68. Waste-bordered mountains of the Arizona Highlands 248 

69. Bradshaw Mountains 252 

70. Ute Mountains 257 

71. Mesa Verde, southwestern Colorado 259 

72. Relief features of the High Plateaus of Utah 262 

73. Former glacier systems of the Wasatch Mountains 266 

74. Morainic ridges near the mouth of Bell Canyon, Wasatch Mountains 267 

75. Sections of the Colorado Plateaus 268 

76. Section of the Mogollon Mountains and Mesa 273 

77. Zuni Plateau 274 

78. Canyon of the Dolores 281 

79. Black Point Monocline, Colorado Plateaus 282 

80. Cross-profile of the Grand Canyon of the Colorado River 285 

81. Topographic profile in relation to rainfall distribution from southwest to 

northeast across the three physiographic provinces of Arizona 286 

82. Relief map of the Henry Mountains 291 

83. Timber zones on San Francisco Peaks, Arizona 293 

84. Mesa forest of western yellow pine in the Mogollon Mountains 295 

85. Mountain systems and ranges and intermontane trenches, northern Rockies 299 

86. Location map of a part of the northern Rockies 299 

87. East-west section, showing flat floor and steep bordering slopes of a typical 

intermontane trench 301 

88. Cceur d'Alene Mountains, looking from above Wardner 303 

89. Coeur d'Alene Mountains, looking toward the crest of the range 303 

90. Cabinet Mountains, Idaho 305 

91. Topographic and structural section across the front ranges in Montana. . . 307 

92. Map of Great Plains and front ranges, western Montana 308 

93. Hogback type of mountains border, Lewis and Clarke National Forest, 

Montana 309 

94. A part of the Lewis Mountains, western Montana 311 

95. Mount Gould, Lewis Range, Montana • . 313 

96. A normally eroded mountain mass not affected by glacial erosion 316 

97. The same mountain mass as in Fig. 96, strongly affected by glaciers which 

still occupy its valleys 316 

98. The same mountain mass as in Fig. 97, shortly after the glaciers have 

melted from its valleys 316 

99. Effects of slope exposure on forest distribution, western Montana 318 

100. Map showing effects of slope exposure on forest distribution, western Mon- 
tana 318 

loi. View south across Salmon River Canyon 321 



LIST OF ILLUSTRATIONS xix 

Figure Page 

102. Bitterroot Mountains and Clearwater Mountains 321 

103. Map of a part of Bitterroot Mountains, Idaho and'Montana 325 

104. Map of the central Rocicies 330 

105. East and West Boulder plateaus 333 

106. Absaroka Range 336 

107. Laramie Plains 338 

108. Terrace and escarpment topography, Green River Basin 340 

109. Hogback topography of inclined beds, southwestern Wyoming 341 

no. Mountains of the Encampment district, south-central Wyoming 343 

111. Stereogram and cross-section of the Uinta Mountains arch 346 

112. Glacier systems of the Uinta Mountains in the Pleistocene 348 

113. Section across highest part of Bighorn Mountains 349 

114. East side of limestone front ridge of Bighorn Mountains, Wyoming 350 

115. Wall at head of cirque. Bighorn Mountains 352 

116. Former glacier systems of the Bighorns 353 

117. Map of the southern Rockies 356 

118. Generalized east-west section near Boulder, Colorado 357 

119. Cross folds on eastern border of Colorado Range 358 

120. West Spanish Peak 360 

121. Longitudinal profiles of five prominent ranges in the Rocky Mountain 

province 363 

122. Section on the common border of Great Plains and southern Rockies 364 

123. Old mountainous upland of the Georgetown district, Colorado 366 

124. Topographic profile and distribution of precipitation across the Wasatch 

and the southern Rockies 369 

125. Extent of the former glacier systems in parts of the Park (east) and the 

Sawatch (west) ranges of Colorado 371 

126. Landslide surface below Red Mountain, near Silverton, Colorado. . . . . . . . 375 

127. Looking down La Plata Valley from the divide at the head of the valley. . 377 

128. Western summits of La Plata Mountains 377 

129. Mount Wilson group 379 

130. Part of Needle Mountains, Colorado 380 

131. Cross section of San Luis Valley 383 

132. Looking eastward from Hunt Springs across the north end of San Luis 

Valley 384 

133. Mountain ranges of the Trans-Pecos province 388 

134. Era Cristobal Mountains, New Mexico 389 

135. East-west section across the Trans-Pecos Highlands north of El Paso, Texas 390 

136. Fault-block mountain in the Trans-Pecos Highlands, Texas 391 

137. Caballos Mountains, New Mexico 392 

138. Section across Franklin Mountains 393 

139. East-west section across Franklin Mountains, Texas 393 

140. Fisher's Peak and Raton Mesa 594 

141. Eastern border of the Rockies 395 

142. Mesa de Maya, south-central Colorado 396 

143. Valley of Rio Grande, El Paso, Texas 400 

144. San Mateo Mountains, Trans-Pecos Highlands 402 

145A. Timber belts, Capitan Mountains, New Mexico. 403 

145B. Range and development of tree species in Lincoln National Forest, Trans- 
Pecos province 404 

146. Geologic map of the Texas regions 406 

147. Topographic and structural sections across the Great Plains 407 

148. Glacial features, northern Great Plains 412 

149. Details of Badlands, Nebraska 415 

150. Physiographic subdivisions of Texas and eastern New Mexico 417 

151. Structure of the Tertiary deposits of the High Plains 418 

152. Typical view of the High Plains of western Kansas. 418 

153. Typical border topography of the High Plains 422 

154. Erosion escarpment of the High Plains 422 

155. Details of form, eastern border of the High Plains, Texas 423 

156. Precipitation in the Te.xas region 424 



XX LIST OF ILLUSTRATIONS 

Figure Page 

157. Vegetation of the Texas regions 426 

158. Llano Estacado, Edwards Plateau, and adjacent territory 431 

159. Summits of the Lampasas Plain, Texas 432 

160. Summits of the Callahan Divide on the Great Plains of Texas 433 

161. Diagrammatic representation of a divide of the Lampasas Cut Plain 435 

162. Edwards Plateau, Balcones Fault Zone, Black Prairie 435 

163. Escarpment timber of the Edwards Plateau 437 

164. Ideal east-west section across the Black Hills 440 

165. Western slope of Black Hills ' 441 

166. Devil's Tower 444 

167. Map of the Little Belt Mountains 447 

168. Map of the Highwood Mountains, Montana 450 

169. The Ozark region and surrounding province , 452 

170. Topography of the Ozark region 453 

171. Section across the Ozark region 454 

172. Mixed hardwoods, etc., in typical relation to topography, Arbuckle Moun- 

tains, Oklahoma 457 

173. Border topography, Wichita Mountains, Oklahoma 458 

174. Typical view of Prairie Plains 461 

175. North-south section of Prairie Plains near Tishomingo, Oklahoma 464 

176. Centers of ice accumulation 465 

177. Four drift sheets of Wisconsin 470 

178. Distribution of glacial moraines and direction of ice movement in southern 

Michigan and northern Ohio and Indiana 471 

179. Glacial map of northern Illinois 472 

180. Wisconsin ice lobes about the Driftless Area 473 

181. Relations of the drift sheets of Iowa and Northern Illinois 473 

182. Southern limit of the Pleistocene ice sheet and distribution of moraines of 

the Dakota glacial lobe. North and South Dakota 474 

183. Old and new channels of the Mississippi at the upper rapids 475 

184. Profile across Lake Michigan 476 

185. Drainage history of the southern Great Lake district 479, 480 

186. Superior ice lake and glacial marginal Lake Duluth. = 482 

187. Lake Duluth at its greatest extent and the contemporary ice border 482 

188. Isobasic map of the Algonkian and Iroquois beaches 484 

189. Map of extinct Lake Agassiz and other glacial lakes 484 

190. Distribution of prairie and woodland in Illinois 490 

191. Cross Timbers of Texas 493 

192. Driftless Area of Wisconsin 496 

193. Diagrammatic section in the Driftless Area 496 

194. Diagrammatic section of Martha's Vineyard 506 

195. Relative positions of ice during the two stages of the Wisconsin glaciation. . . 507 

196. Section showing the relation of outwash to terminal moraine 508 

197. Glacial outwash topography. Long Island 509 

198. Cross section of Long Island 509 

199. Terminal moraines, soils, and vegetation of Long Island 511 

200. Characteristic growth of pitch pine and scrub oak, eastern Long Island. . . 512 

201. Effects of repeated fires on soil and vegetation. Long Island 512 

202. Typical growth of hardwood on the clayey portions of the Harbor Hill 

moraine. Long Island 513 

203. Scattered growth of pitch pine and scrub oak on the sandy portion of the 

Ronkonkama moraine south of Riverhead, Long Island 513 

204. Sand reef, salt marsh, and coastal plain upland, coast of New Jersey 515 

205. Swampy divides in eastern Maryland between the Chesapeake and the 

Atlantic 517 

206. Cypress trees of the Dismal Swamp 518 

207. Albemarle and Pamlico Sounds, east coast of North Carolina 519 

208. Chesapeake Bay and Delaware Bay and the principal bays tributary to 

them 519 

209. Finger-like extensions of the Mississippi delta 525 

210. The lower alluvial valley of the Mississippi 527 



LIST OF ILLUSTRATIONS xxi 

Figure Page 

211. Coastal features of Texas, long, simple sand reefs enclosing narrow lagoons 529 

212. Prominent topographic features of the Gulf Coastal Plain 532 

213. Cross section of the Gulf Coastal Plain in Louisiana and southern Arkansas 533 

214. One of the timber jams composing the great Red River raft 535 

215. Lakes of the Red River valley in Louisiana 535 

216. Timber deadened in temporary raft lake 536 

217. One of the Red River rafts 536 

218. Map showing diversion of Red River below Alexandria, La 537 

219. Growth and drainage of the raft lakes at the Arkansas-Louisiana state hne 538 

220. Principal lakes of Florida 544 

221. Swamp lands of the United States 549 

222. Rock types and boundaries, Laurentian Plateau. . . 554 

223. The Laurentian Plateau 556 

224. The Laurentide Mountains 558 

225. Lake region of North America 565 

226. Details of drainage in a portion of the Laurentian Plateau 566 

227. View on the shore of Lake St. John, Quebec 568 

228. Distribution of the dominant conifers in Canada and eastern United States 571 

229. Typical drainage irregularities in the Lake Superior Highlands 572 

230. Boundaries of the Superior Highlands 573 

231. Deformation of strata near Porcupine Mountain, northern Michigan 575 

232. Structure and topography of the southern border of the Superior Highlands 576 

233. Character and relations of the pre-Cambrian and Cretaceous peneplains in 

northern Wisconsin 577 

234. Plateau-like western portion of the Adirondack Mountains. 580 

235. Rectangular pattern of relief and drainage lines in fault-block mountains 

of the eastern Adirondacks 582 

235a. Drainage map of the Appalachian region 587 

236. Structural relations of the various parts of the Appalachian System. ..... 589 

237. Axes of deformation, southern Appalachians 593 

238. Physiographic map of southern Appalachians 595 

239. Curve illustrating the relation of topographic relief to lithologic compo- 

sition in the southern part of the Appalachian System 598 

240. Probable preglacial drainage of western Pennsylvania 599 

241. Maximum stage of Lake Passaic 601 

242. Pisgah Mountains from Eagles Nest near Waynesville, N. C 605 

243. Geologic structure of the Appalachian region 607 

244. Roan Mountain, Tennessee 608 

245. The Asheville Basin. 611 

246. Distribution of forests and cleared land, southern Appalachians 613 

247. Grassy "bald" and border of spruce forest. White Top Mountain, Virginia 613 

248. Protection against erosion by parallel ditches 617 

249. Erosion checked by covering galleys with brush, Longcreek, Virginia 617 

250. Erosion checked by brush dams. Walnut Run, N. C 618 

251. Plateau and escarpment of the Blue Ridge 620 

252. Blue Ridge, Catoctin Mountain, and Bull Run Mountain in Virginia 621 

252a. Cross section of the Catoctin Belt, western border of Virginia 622 

253. Cross section of the Catoctin Belt, western part of Virginia 622 

254. Local development of Triassic rock in the older Appalachians 627 

255. Relations of the igneous rocks to the sedimentary strata (Newark) in New 

Jersey 628 

256. Palisades of the Hudson 628 

257. The four crystalline prongs of the older Appalachians ■ 630 

258. Terminal moraine and direction of ice movement in the vicinity of New 

York 632 

259. Characteristic terminal-moraine topography 633 

260. Profile across central New England 637 

261. Section south of Blue Hill, Maine 646 

262. Forest growth on a steep and rocky New England hillside, Jamaica Plain, 

Mass 652 

263. Relation of the Connecticut Valley lowland to the bordering uplands 654 



XXU LIST OF ILLUSTRATIONS 

Figure Page 

264. The geologic and physiographic history of the Connecticut Valley lowland 

and adjacent portions of the bordering uplands — A, B, C, D 655, 656 

265. Displacement of trap ridges near northern end of West Rock Ridge 657 

266. Inferred Cretaceous overlap on the southern shore of Connecticut. .^ 658 

267. The North Haven sand plain or "desert'' 661 

268. Relief map of the central part of the Appalachian System 665 

269. The half-cigar-shaped mountains developed on the hard rocks and the 

arches formed by the beds of an anticline 674 

270. The canoe-shaped ridges of hard rocks and the arches formed by the beds 

of a syncline '. 674 

271. The development of anticlinal valleys and synclinal mountains from an 

original consequent drainage in a region with Appalachian structure. . 676 

272. Varying positions of the plane of base-leveling to hard and soft strata and 

their relation to anticlinal and synclinal mountains, 677 

273. Cross section from the Hudson Valley across the Rensselaer Plateau and 

the Taconic Range 680 

274. Geologic and physiographic map of the Taconic region 680 

275. North-south section across the northern edge of the Appalachian Plateaus 686 

276. Warped surface of the early Tertiary (Harrisburg) peneplain of the central 

Appalachians 688 

277. Section illustrating the terraces of the Ohio Valley 689 

278. Present and pre-Pleistocene courses of Monongahela and Youghiogheny 

rivers 690 

279. Distribution of morainal deposits and direction of ice movement in western 

. New York 693 

280. Maturely dissected Allegheny Plateau in West Virginia 694 

281. Map of region between Cumberland Plateau and Highland River 699 

282. Northern portion of the Cincinnati arch 702 

283. Section across the Nashville Basin of Tennessee and the country adjacent 704 

284. Physiographic belts in central New York 708 

285. Map of portion of New York 710 

286. 287, 288. Proglacial lakes, Finger Lake district, New York 712, 713 

289. Channels and deltas of a part of the ice-border drainage between Leroy and 

Fishers, New York 714 

290. Gulf channel, looking southeast (downstream) near mouth of channel. . . . 715 

291. Roc drumlins or drumloids 717 

292. Topographic types, central New York 718 



LIST OF PLATES 

Frontispiece. Zone Map of North America. 

Plate I. Climatic and Life Provinces of North America. 

Plate II. Colorado Plateaus. 

Plate III. Southern Appalachians. 

Plate IV. Physiographic Map of the United States. 

Plate V. Geologic Map of North America. 



FOREST PHYSIOGRAPHY 



PART ONE 

THE SOIL 



CHAPTER I 

THE IMPORTANCE, ORIGIN, AND DIVERSITY OF SOILS 
The Soil in Relation to Life 

Men whose work brings them into touch with the soil and its relation 
to hfe do not employ the phrase "mother earth" in a casual sense. 
The great hosts of plant and animal life that people the lands in large 
part have their origin in or draw their support from the cover of land 
waste whose upper layers are the soil. They are, directly or indirectly, 
the dependent children of the earth. Viewed from such a standpoint 
the soil is not mere dirt, a substance to be despised, a synonym for 
filth, but a great storehouse of energy, a great home, a bountiful mother. 
Countless billions of micro-organisms — the bacterial flora — throng its 
dark passageways while the roots of countless higher plants ramify 
through it in eager quest for food and water. Only less numerous are 
the earthworms, insects, and burrowing animals that delve into it for 
food as well as for shelter. To supply all these needs is no mean func- 
tion ; it is probable that no other planet in our solar system has so large 
an endowment of life-giving, life-supporting soil; the evolution of the 
life of the earth would have been on far lower levels if the endowment 
had not been so generous. 

The Soil and the Forest 

From the standpoint of the forest the soil is a factor of great impor- 
tance. The home of the tree is the soil and the air; and a forester, whose 
chief concern is the tree, requires a somewhat comprehensive knowledge 
of these two elements of the environment of every forest. Without 



2 FOREST PHYSIOGRAPHY 

soil in some amount tree growth of any kind is impossible, although 
the amount required to produce a poor growth may be very small. 
Low forms of vegetation,: such as Hchens, mosses, and shrutjs of many 
varieties, may find life possible in a region where there appears to be 
practically no soil; but a careful examination will usually disclose rock 
pockets partially filled with small quantities of soil, tiny crevices that 
contain particles of dust, and joints in greater or lesser number that 
have caught soil fragments washed from the adjacent surfaces almost 
as fast as formed. These accumulations afford a foothold for the lower 
forms of vegetable life which tend to disintegrate both soil and rock and 
further to increase the amount of available soil. Ordinary weathering 
will tend toward the same result, and if the climatic conditions, the relief, 
etc., are favorable, a soil cover capable of sustaining a denser growth 
of vegetation of a higher order will eventually be formed. In time 
and through the gradual development of a soil cover a dense forest may 
grow on what was in a preceding portion of a geologic period a bare 
rock terrane. 

While the broad relation of the soil to the forest is thus readily dis- 
tinguishable, the finer relations are often difficult of determination and 
there are many physical conditions that evoke no recognizable response 
in the forest world. A study of the maps, Fig. 23 and Plates IV and V, 
representing respectively the forest regions of the United States, the 
physiographic provinces and the geologic formations, will enable the 
student of forest physiography to appreciate at once that the physio- 
graphic features and related soil types are of more local development 
than the broad forest types which they support; and that the finer 
distinctions between soil types are of little value in understanding the 
range of a given forest type, however directly they may affect the wel- 
fare of the individual tree by modifying its habitat. In short, it may be 
said that the conditions which limit either the growth or the distribu- 
tion of most forest species are so extreme that they embrace or overlap 
a large number of physical subdivisions. 

In general plants are rather impartial as to soil unless the soil char- 
acters are of an extreme tj^Dc; relatively few have absolute soil require- 
ments. Competition among forest trees may drive out some species, in 
which case the unsuccessful species can not be described as incapable 
of growth on the soil from which they have been driven; simply, their 
competitors are able better to use the given resources of soil and air. 
It often happens that a given species is markedly tolerant of soil and 
climate except at the limits of its range where competition begets an 
apparent intolerance. 



ORIGIN AND DIVERSITY OF SOILS 3 

It is concluded that plants possess a peculiar inherent force by the 
exercise of which they directly adapt themselves to new conditions and 
become fitted for existence in accordance with new surroundings. Thus 
plants are thought to have a certain physiologic plasticity or power of 
self-regulation that tends to adjust them to a new environment, a feature 
that goes far in explaining the absence of a rigid control of physiographic 
conditions over forest distributions although an approximate control is 
often manifested.^ The forester, then, requires a scientific knowledge 
of soils and climate, but in the final application of his knowledge to the 
distribution and growth of forests it is often necessary for him to employ 
somewhat broader generalizations than those employed by the geog- 
rapher and the botanist for the special purposes of their sciences. 

The Maintenance of a Soil Cover 

Everywhere on the land we find at work the two forces of soil making 
and soil removal. In regions of aggradation the two tend in the same 
direction; in regions of degradation the soil may be removed as fast as 
formed and bare rock everywhere exposed at the surface; or there may 
be established so delicate a balance between soil formation aind soil 
removal that though the soil cover is continually wasted the process of 
soil formation takes place at an equivalent rate and a covering of soil 
is perpetually maintained. 

The matter of soil formation is of special importance to the people 
of North America, for not only is denudation (chiefly glacial) respon- 
sible for an area of bare, denuded country almost twice as great as that 
of the continent next in order in this respect, Africa, but denudation is 
probably proceeding at a faster rate on our continent than on any of 
the other five. The saving quality of glacial denudation in the past 
has been its occurrence chiefly in mountain regions of the United States 
and in the upper boreal and the arctic regions of Canada where extreme 
climatic conditions would largely offset the advantages of soil.- A 
physiographic map of the United States, Plate IV, appears to show that 
approximately one-fifth to one-sixth of the total area is now undergoing 
alluviation; everywhere else, no matter what process has been active 
in the immediate geologic past, the surface is now being eroded. The 
action is so slow in some places as to be exceeded by the rate of rock 
decay, and in such cases no fear need be entertained for the safety of 

1 See especially, V. M. Spalding, Distribution and Movements of Desert Plants, Carnegie 
Inst. Pub. No. 113, igog; also E. Warming, (Ecology of Plants, Ox. ed., 1904, pp. 370-372. 

^ For an outline presentation of the balance of soil-making and soil-destroying forces that 
have produced the main soil types now at the surface of the earth see the table, p. 25. 



4 FOREST PHYSIOGRAPHY 

the soil; in other localities the action is rapid and disastrous and its 
checking should be a matter of the gravest concern. As early as 1890, 
Shaler ^ estimated that the soils of about 4000 square miles' of country 
had been impoverished through wasteful agricultural methods, repre- 
senting a loss of food resources sufficient to support a million people; and 
that at least 5% of the soils which at one time proved fertile under 
tillage "are now unfit to produce anything more valuable than scanty 
pasturage." To us of a later generation this figure appears gratifyingly 
small beside the figure that would express the deplorable ruin of the 
past quarter century of reckless timber cutting and baneful neglect of 
fields abandoned by the upland farmer. 

The forest is an important factor in soil erosion because it plays a 
considerable part in the flow of water by which such erosion is effected. 
The inequalities of the forest floor offer many mechanical obstacles 
to the flow of surface waters. Innumerable pools of water collect in 
hollows and are gradually absorbed by the underlying soil instead of 
running off at the surface. The leaf canopy catches and reevaporates 
about 12% of the rainfall, while 10% of it runs along the tree trunks 
and reaches the ground by a circuitous course. The forest litter, 
the moss-covered and leaf-strewn ground, is capable of absorbing water 
at the rate of from 40,000,000 to 50,000,000 cubic feet per square 
mile in 10 minutes, — -water whose progress is delayed by some 12 to 
15 hours after the first effects of a heavy freshet have passed.^ 

While the forest thus plays an important part in the maintenance 
of a soil cover and in the better equalization of the run-off of streams, 
it would be a mistake to assume that it is the only agent which accom- 
plishes these highly beneficial results. It is scarcely more necessary to 
know that deforestation may permit a precious soil cover to be wasted 
than it is to imderstand that many other types of vegetal covering 
besides the forest effect these desirable results. Of the same order of 
importance is the fact that the effects that follow upon deforestation are 
not equally harmful upon all types of topography and soil. If these con- 
clusions are true it is necessary that the soil, the topography, and the 
secondary vegetative forces of a given region be evaluated before the 
statement is made that excessive soil erosion is the necessary correlative 
of deforestation. 

That the soil is protected by many vegetal types other than the forest 
is now a well-established fact. The high alpine meadows of the Pacific 

' N. S. Shaler, The Origin and Nature of Soils, 12th Ann. Rept. U. S. Gaol. Surv., pt. i, 
1890-1891, p. 333. 

2 B. E. Fernow, Relation of Forest to Water SuppHes, in Forest Influences, Bull. U. -S. 
Dept. Agri., Forestry Division, No. 7, 1902, p. 158. 



ORIGIN AND DIVERSITY OF SOILS 5 

Cordillera consist in many cases of a thick turf which supports natural 
grasses of luxuriant growth. The interlacing roots of the grasses in many 
situations bind the soil past all reasonable possibility of excessive erosion, 
the stems of the grasses impede the run-off by breaking up in one locality 
any incipient streams formed in another locality exceptionally favorable 
to concentration of run-off, the whole grass cover breaks the force of the 
falling rain and prevents erosion. Added to these is the influence of 
ponds and lakes of glacial origin in the higher situations. The retention 
of the soil above timber line on the Beartooth Plateau, southwestern 
Montana, is attributed to such a combination of grass cover and stor- 
age basins;^ it was as natural a result that gullying should follow over- 
grazing of these meadows as that evil results should follow deforestation 
in the well-known case of the Southern Appalachians. The binding of the 
soil and the checking of erosion are also effected by brush and vines which 
in moist regions may spring up in a few years following deforestation 
and form an almost impenetrable covering. Such a tangle of vegetation 
offers even greater resistance to the surface flow of water than does the 
vegetation of a forest, besides permitting the formation of snowdrifts, 
one of the most important forms of surface water storage.^ 

The retention of rainfall by the mosses that cover the hill slopes of the 
Laurentian Plateau, a feature especially well developed in the Labrador 
peninsula, diminishes the run-off and equalizes it to a degree far exceed- 
ing that of the thin spruce forests of the region. Even the steepest 
slopes are slippery with loose dripping Sphagnum moss, whose effects 
obviously exceed those of the most porous forest floor. The very 
existence of a steep hillside bog is in itself proof of an unusually powerful 
retentive effect of the moss cover upon both soil and run-off. 

All of these consequences are subject to changes in degree depending 
upon variations in soil and topography. If the soil is very porous the 
imbibition of rain water is rapid and run-off and erosion are correspond- 
ingly lessened; if the soil is compact there is little absorption, and 
run-off and soil erosion are more active. A hill-and-valley country, 
one consisting entirely of slopes of strong gradient, such as the well- 
dissected Allegheny Plateau, has a high percentage of run-off and soil 
erosion, for almost every drop of water falls upon a slope and begins 
a downhill movement the moment it strikes the surface. A flat surface 
like the till plains of central Indiana or the outer part of the coastal 

1 J. B. Leiberg, Forest Conditions in the Absaroka Division of the Yellowstone Forest Re- 
serve, Montana, Prof. Paper U. S. Geol. Surv. No. 29, 1904, pp. 15-19. 

' J. C. Stevens, Water Powers of the Cascade Range, pt. i, Southern Washington, Water- 
Supply Paper U. S. Geol. Surv. No. 253, 1910, p. 16. 



6 FOREST PHYSIOGRAPHY 

plain of South Carolina absorbs a high proportion of the rainfall, and 
soil erosion is of trifling importance. Combinations of these factors are 
both numerous and variable. A part of the southern slope of Long 
Island is a natural prairie unforested even before the coming of the 
whites. It bears almost no signs of erosion, and such as occur had in 
most cases a very special origin. The absence of erosional features 
is not surprising when the low gradient of the plain, lo feet per mile, 
and the high porosity of the sand are taken into account. These flat- 
lying porous sands absorb from 60% to 75% of the rainfall, perhaps 
as great a value as that found on any other arfea of equal size in the 
eastern half of the United States. 

In New England it has been noted that the quick-growing brush and 
the special qualities of the glacial soil prevent the undue erosion of de- 
forested hill slopes in the Berkshires where the relief is so strong that 
landslides sometimes occur. The pebbles and bowlders of the till con- 
stantly divert the run-off and lessen its velocity, while the bottoms of 
ravines sunk into the till are in a measure protected from erosion by a 
pavement of stones derived from the till. In many cases in western 
Massachusetts and Vermont and New Hampshire steep mountain 
slopes "have been several times stripped of their forest growth with 
little, though doubtless some, injury to the soil," and "the mountain 
streams are beautifully clear except immediately after a heavy 
rain."i 

The large number of rock ledges that occur in this region contribute to 
the same effect. The soil is thin, and irregularities of the underlying 
bed-rock assist in holding it in place not only by physically retaining it 
but also by preventing the streams held upon the projecting rock ledges 
from expending the whole of their erosive energy upon its loose material. 

The effect of the forest upon the run-off alone is extremely difficult 
of determination, for soil and topography are in this respect of much 
greater importance. That forests tend to conserve the run-off is clear; 
their effects in individual cases, however, may be so small as compared 
with the effects of soil and topography as to be overshadowed by the 
latter. 

"Donner und Blitzen River, in central Oregon, is a very uniform stream with a well-main- 
tained summer flow, but its area does not produce a tree, except here and there a juniper. On 
the other hand, Silvies River, which exists under the same climatic conditions as Donner imd 
Bhtzen River and discharges its waters into the same lake, is anything but uniform in its flow, 
although its drainage area is heavily forested. Niobrara and Loup rivers, in Nebraska, are 
very uniform in flow, but there is hardly enough timber on both areas to build a cabin. Nearly 

1 H. F. Cleland, The Effects of Deforestation in New England, Science, n. s., vol. 32, 1910, 
pp. 82-83. 



ORIGIN AND DIVERSITY OF SOILS 7 

all the streams of western Oregon and Washington are subject to enormous floods, and all run 
comparatively low in summer, yet no streams in the world have more densely forested drainage 
areas." i 

The conclusion that forests are not a guaranty of uniform stream flow, 
in spite of the fact that they tend in the direction of uniformity, does not 
diminish the interest of students in such influence as forests do exert, 
since theirs is a controllable influence. Man can not greatly modify the 
porosity of the soil or the slopes of the land, and the effects that follow 
upon these causes are therefore irremediable; but man may save a forest 
or plant one and thus mitigate effects which he can not wholly prevent. 
In precisely those regions where run-off and soil erosion are most ex- 
treme through unfavorable topographic and soil conditions, man may 
find it possible to preserve a tolerable state of affairs by saving the 
forest from destruction. In regions where the conditions are critical 
the destruction of the forest may mean the quick destruction of the soil, 
its preservation the preservation of the soil and the indefinite occupa- 
tion of the region by man. 

The retaining influence of the forest on the soil is most strikingly 
exhibited where the balance between soil formation and soil removal is 
delicately established and may be easily destroyed. An extreme in- 
stance is Kanab Creek, Utah, where the burning of the forest and the 
overgrazing of the pastures have resulted in torrent conditions. The 
tributaries have become deep washes, many new and deep gulches have 
been formed, dams and bridges have been destroyed by the floods and 
coarse gravel deposited on formerly arable valley lands.- 

It is of importance, then, to examine at the outset the relations of soil 
denudation and soil accumulation, that we may be the better prepared 
to study those forces which tend to bind and partially to retain the 
covering of soil; not only that forests themselves may be perpetuated, 
but also that the flood-plain soils on the borders of the forests may 
be adequately preserved and the natural advantages of the waterways 
retained. 

Soil-making Forces ^ 

The complex cover of rock waste which we call the soil is the product 
of a great number and variety of forces. Only the principal ones are 
here outlined. 

1 J. C. Stevens, Water Powers of the Cascade Range, Southern Washington, Water-Supply 
Paper U. S. Geol. Surv. No. 253, 1910, p. 17. 

2 H. S. Graves, The Forest and the Nation, American Forestry, vol. 16, 1910, p. 608. 

3 The section on soils is necessarily brief and somewhat technical and assumes on the part of 
the student a knowledge of ordinary rocks and rock-making minerals as well as an elementary 
knowledge of chemistry. Those students who are deficient in such knowledge should consult 



8 FOREST PHYSIOGRAPHY 

OXIDATION. 

CARBONATION. 

HYDBATION. 

SOLUTION. 

MECHANICAL ACTION OF WATER AND ICE. 

TEMPERATURE EFFECTS. 

WIND. 

BACTERIA. 

ANIMALS AND THE HIGHER PLANTS. 

OXIDATION 

Oxygen is the most active element of the air, and the process of oxi- 
dation is of great importance in reducing rock masses to soils. The 
action is perceptibly manifested only in rocks containing iron either as 
a sulphide, a carbonate, or a silicate. Of these the sulphides are changed 
to sulphates which are soluble and may be removed in solution. 
The most common minerals attacked are ferrous carbonate associated 
with the carbonates of lime and magnesia and the silicates of mica, 
amphibole, and pyroxene. The minerals become gradually decomposed 
through oxidation and disintegrate into unrecognizable forms. The 
oxidation of the iron-making minerals of a rock is always attended by 
increase in bulk, and when this takes place in cracks and crevices it 
tends, like the freezing of water, to widen the cracks and to increase the 
surface exposed to attack. In general the action of the air in soil 
formation is of secondary importance and depends chiefly on the oxida- 
tion of the lower to the higher basic forms. The ferrous and ferroso- 
ferric oxides are converted into ferric oxide or its hydrate limonite, 
iron rust, which gives to soils containing much iron their characteristic 
reddish or yellowish colors. 

The presence of ozone ^ in air without doubt causes it to have a more 
active oxidizing effect. Ozone is present in considerable quantity in 
the air only when the air is free from organic impurities and products 
of decay. The average amount of ozone in a hundred cubic meters of 
air is 1.4 mg., but the amount may be doubled after thunderstorms.^ 

Merrill, Rocks, Rock-weathering and Soils, 1897. For purposes of brief inspection of the 
mineralogical composition of ordinary rocks and the chemical composition of rock-making 
minerals the tables in Appendix C in this book should be consulted, and a text-book of 
Lithology such as Pirsson, Rocks and Rock-forming Minerals, 1909. 

' Ozone is a very active form of oxygen in which the molecules consist of three atoms of 
oxygen instead of two atoms as in a molecule of ordinary oxygen. It is formed by silent elec- 
trical discharges, and is chemically unstable, readily parting with one of its atoms, hence chemi- 
cally active. 

2 J. Hann, Handbook of Climatology, 1903, pp. 80-81. 



ORIGIN AND DIVERSITY OF SOILS 9 

The amount of ozone in the air is determined by the rate of change in an 
easily oxidized substance — not a very accurate method.^ Ebermayer 
emphasizes the more powerful oxidizing effects of ozone in the air and 
its formation in the forest in unusual amounts.^ 

CARBONATION 

The oxidation of organic materials (both plant and animal remains) 
by bacteria and oxygen in the zone of weathering produces a concentra- 
tion of carbon dioxide near the surface. The degree of concentration 
of this gas in the zone of weathering is appreciated by comparison of 
the soil air with the atmosphere. The amount of carbon dioxide in 
the atmosphere is 45 parts in 10,000 by weight; the amount in soil air 
or soil gases is represented in the following table: 



AMOUNT OF CARBON DIOXIDE IN SOIL AIR^ 



Derivation 


Parts by weight 
in 10,000 




38 
124 
130 
270 
543 






Air from pasture soil 

Air from soil rich in humus 



The carbon dioxide in the soil is the agent in the important weathering 
process known as carbonation, by which is meant the union of carbonic 
acid with bases in the formation of carbonates. It is dominantly accom- 
plished by the substitution of carbonic for silicic acid. To some extent 
carbonates are also formed (i) by the substitution of carbonic acid for 
other acids, e.g., phosphoric acid, and (2) by the union of carbon dioxide 
with oxides not united with other acids, e.g., ferrous oxide in magnetite.^ 

The process of carbonation takes place on a vast scale. It is most 
rapid in the tropics, takes place at a moderate rate in temperate lands, 
and is least important in the frigid zones and in arid regions. It has a 
direct relation to the amount of vegetation, since it is chiefly through the 
decay of the vegetation that carbon dioxide is supplied for the reaction 
involved in carbonation. On the other hand a soil containing carbon- 

• W. M. Davis, Elementary Meteorology, 1898, p. 5. 

2 E. Ebermayer, Lehre der Waldstreu, etc., 1876, p. 202. 

3 Boussingault and Levy, quoted by G. P. Merrill, Rocks, Rock-weathering and Soils, 
1897, p. 178. 

* C. R. Van Hise, A Treatise on Metamorphism, Mon. U. S. Geol. Surv., vol. 47, 1904, 
P- 475. 



lO FOREST PHYSIOGRAPHY 

ates is ordinarily fertile and supports an abundant vegetation. The 
surface vegetation and the soil carbonates are therefore mutually inter- 
active and helpful. The cumulative effect of the act of carbonation 
would therefore appear to be constantly increasing amounts of carbon- 
ate substances. But this tendency is offset or matched by the libera- 
tion of silica in the process of carbonation; about one and one-third 
times as much silica is released from the silicates as there is carbon 
dioxide combined in the carbonates.^ 



HYDRATION 

The action of hydration is the union, of^water with chemicaLcom^ 
.p^ojinds- injthe produclion of hydrous minerals. It is the most extensive 
reaction in the zone of weathering and next to carbonation the most 
important. It affects practically all of the anhydrous silicate minerals 
of the igneous, sedimentary, and metamorphic rocks to some degree, 
and many of them to a great degree. The decomposition products of 
the rock minerals are almost all strongly hydrated, such as the zeolites, 
chlorites, and kaolin in the silicate class and aluminum and iron among 
the oxides. 

The action of hydration is always accompanied by the liberation of 
great quantities of heat and by increase in bulk. It is calculated that 
the transition of a granite rock into arable soil, provided such transition 
takes place without loss of material, is attended by an increase in bulk 
of 88%. In rocks as a class hydration effects volume increases which 
range from a very small per cent to i6o% (corundum to gibbsite). 
In general the increase is less than 50%. Such volume increases 
prevent complete hydration at any great depth below the surface; 
partly hydrated rock when artificially exposed at the surface, as in 
railway cuttings, may become completely hydrated at so rapid a rate 
as to expand greatly in volume and soon disintegrate. Notable in- 
crease in bulk does not follow if the pore space is ample; if the pore 
space is small and the rock dense the action "is either incomplete or 
involves great increase in bulk. 

Commonly hydration takes place in connection with carbonation and 
solution. In so far as soil water is consumed in the formation of new 
(hydrous) minerals it can not be used in the process of solution; the 
amount so consumed is, however, but a small part of the whole, and 
solution is therefore a companion process of hydration. 

1 C. R. Van Hise, A Treatise on Metamorphism, Mon. U. S. Gaol. Surv., vol. 47, 1904, 
p. 480. 



ORIGIN AND DIVERSITY OF SOILS II 

SOLUTION 

WATER AS AN AID TO CHEMICAL ACTION 

Water is the most important weathering agent, not only because of 
its direct effects but also because its presence conditions all phases of 
weathering, such as hydration, etc. It has so great a dissolving power 
that few substances found in rocks are wholly insoluble in it, while in 
water charged with acids of various sorts many rocks are readily soluble 
and all are somewhat soluble. The number of such acids is small, but 
their action is so general that they powerfully aid solution in reducing 
rocks to soil. Nitric acid is present in some amount in rainfall, in 
surface waters, and in the soil water, in which it may be supplied in 
small quantities by the action of bacteria. Sulphuric acid may be 
derived in somewhat the same manner; an important source in some 
regions is iron pyrites, which on decomposition may yield free sulphuric 
acid. It is altogether probable that many if not all soils constantly 
receive small amounts of sulphuric acid, and it is possible that in some 
cases the solvent action of this acid on the mineral constituents of the 
soil may become important.^ Among these substances is chlorine the 
amount of which in the air varies with the distance from the sea and is 
greatest at the seashore. On the island of Barbados ii6 pounds of 
chlorine are contributed annually to each acre.^ Two or three extractions 
of soils, however, seldom show the presence of any free acid other than 
carbonic acid. 

Carbon dioxide, which is the basis of carbonic acid, is contained in all 
natural water and in rainfall so that all percolating waters are real acid 
solvents and exercise a far-reaching effect, a fact now universally recog- 
nized. That dissolved carbon dioxide may act directly as an acid, thus 
increasing the solvent power of the water in which it is contained, is 
probable.^ The destructive action of water charged with carbonic acid 
is most strikingly exhibited in limestone but it is not confined to this type 
of rock; even quartzose rocks of the ordinary kinds are attacked by it and 
granite and related rocks are rather quickly affected. Its effect both in 
the soil and in the zone of weathering ■* generally is due largely to a reduc- 
tion of the mass of the hydrates of the hydrolyzed bases by the formation 
of bicarbonates. The result of its action upon the feldspars is the forma- 

1 C. R. Van Hise, A Treatise on Metamorphism, Mon. U. S. Geol. Surv., vol. 47, 1904, 
p. 205 et al. 

2 Harrison and Williams, Jour. Am. Chem. Soc, vol. 19, 1897, p. i. 

' Carbon dioxide is soluble in water to the extent of equal volumes at ordinary temperature 
and barometric pressure. 

' The zone of weathering extends from the surface to the ground water (Van Hise, A Treatise 
on Metamorphism, Mon. U. S. Geol. Surv., vol. 47, 1904). 



12 FOREST PHYSIOGRAPHY 

tion of clay, a most essential element of soils from the physical stand- 
point, and the freeing of potash, one of the most essential plant foods. 
In the case of granite rocks the silica set free by the carbonic a,cid remains 
partially or wholly in the resulting soils; in the case of limestones the 
lime at first remains in the form of a carbonate, but potash and soda 
compounds, which are readily soluble in water, are largely carried away 
either by percolating water or absorbed by plants. The action of carbon 
dioxide is also manifest in the formation of carbonates of iron and 
magnesium. 

In certain experiments carried on in the laboratory of the U. S. Bureau of Soils some powdered 
minerals, among which were muscovite and albite, were kept in contact for fourteen months 
with water and certain solutions in parafSn cylinders. Excepting the results obtained with 
albite, those obtained by treatment with water saturated with carbon dioxide are so much 
greater than the corresponding results obtained with pure water that no reasonable doubt 
can exist that the effect of the carbon dioxide is not only to hasten the rate of solution, but 
actually to increase the absolute solvent action of the water. i 

In nature all the elements in the rock and the soil minerals in the 
zone of weathering are being dissolved all the time, but at variable rates 
depending (i) upon the strength and abundance of the active compounds 
in solution and (2) upon the solubility of the constituent minerals. 

WATER AS A CARRIER 

In addition to being the substance necessary for the chemical decom- 
position of nearly all kinds of rocks and soil, water has an important 
influence in removing large amounts of soluble plant food from the soil. 
Nearly five billions of tons of mineral matter are annually carried away 
in solution from the land into the sea, while the amount of sediment is 
many times greater. - 

The amount of nitric acid found in drain water (water that runs off 
through drains, i.e., tiles, etc.) sometimes shows a heavy depletion of 
the land by the leaching out of this highly important substance. In all 
drain water lime is found to be leached out most abundantly, mainly 
in the form of bicarbonate. Magnesia is next in order, then soda and 
other substances of minor value. Potash is present in drain water in 
small amounts. Carbonic acid is the most abundant of the acids found 
in such water, and chlorine and silicic acids are next in order. 

MECHANICAL ACTION OF WATER AND ICE 

An important mechanical effect of water is exhibited during rain 
storms when the erosion of soil on all slopes and its rapid erosion on 
unprotected steep slopes occur and may lay bare the rock surface 

1 Cameron and Bell, The Mineral Constituents of the Soil Solution, Bull. U. S. Bur. Soils 
No. 30, 1905. 

2 E. W. Hilgard, Soils, 1906, p. 24. 



ORIGIN AND DIVERSITY OF SOILS 13 

and enable other soil- making forces again to act upon the exposed rock. 
Falling raindrops also beat upon and jostle the soil grains or move them 
about upon the rock surface in such manner as to break off smaller 
particles, an action which on flat surfaces may tend to increase the amount 
of soil. 

It has been computed with reasonable accuracy that 783 million tons 
of earth and rock measured as soil are removed each year by erosion 
from the surface of the United States. The amount removed from 
different watersheds varies greatly, not only on account of differences 
in the sizes of the drainage areas but also on account of differences in 
the depth and porosity of the soil, the extent and nature of the vegetable 
cover, the lengths and declivities of the slope, the rainfall, the temper- 
ature, the extent of lakes, etc. In the north Atlantic basin the rate 
is 130 tons per square mile per year; the rate in the Hudson Bay basin is 
28 tons and is the lowest on the continent; the southern Pacific basin 
heads the list with 177 tons. Individually the Colorado River brings 
down the greatest amount of suspended matter; it delivers 387 tons per 
year for every square mile of its drainage basin. Practically no suspended 
matter is transported by the St. Lawrence River, since the water is 
cleared by sedimentation in the Great Lakes. In general the northern 
streams carry much less suspended matter than the southern streams, 
a result due probably to the large number of lakes in the drainage 
basins of the northern streams, the large extent of bare rock outcrop, 
and the hindrances to erosion imposed by soil frozen during a large part 
of the year.^ 

The action of freezing water is due mainly to the expansive force it 
manifests as it passes from water to ice, and has been described as equiva- 
lent to the pressure of a column of ice a mile high, or about 150 tons to 
the square foot. If a given rock contains much water in its pore space 
and is repeatedly subjected to freezing temperatures, the rock will in 
time be disrupted by heavy internal strains. The extent of the strain 
effect depends (i) upon the climate, (2) upon the weather conditions, 
whether uniform or variable, and (3) upon the amount of water con- 
tained by the various kinds of rock, which in turn differs with the nature 
of the minerals and their state of aggregation. 

All rocks when freshly exposed hold by capillary attraction a certain amount of water, 
which occurs largely as interstitial water. The amounts that may be contained are expressed 
roughly as follows: granite, 0.37% by weight; chalk, 20'^; ordinary compact limestone, 0.5% 
to 5%; and sandstones from 10% to 12%; while clay may contain nearly one-fourth its weight 

1 These computations show that the surface of the United States is being removed at the 
average rate of .0013 of an inch per year, or i inch in 760 years. Dole and Stabler, Water- 
Supply Paper U. S. Geol. Surv. No. 234, 1910 (Denudation), pp. 82-83. 



14 



FOREST PHYSIOGRAPHY 



in water. The amount in white chalk is as much as 19% and a piece of such chalk, may be 
shattered into fragments by a single night's frost. The freezing of absorbed water is one of 
the most general sources of disintegration of building stones.' 

In addition to the expansive force of interstitial water when frozen 
is the action of freezing water in the joints of the rock, which tends to 
disrupt large masses from the faces of cliffs and other bare rock surfaces. 

The effect is heightened if freezing 
and thawing alternate in periods 
of short duration. Alternate freez- 
ings and thawngs may be beneficial 
to the soil after formation, because 
the freezing of the water in the pore 
spaces increases the bulk of the 
whole mass of frozen soil, — an in- 
crease which is not immediately 
compensated on thawing, so that 
aeration and root penetration derive 
a certain benefit from the process. 

TEMPERATURE EFFECTS 

While the agencies we have so far 
enumerated are active in nature in 
breaking down rock, soil would be 
formed without such agencies, though 
at a slower rate, through the in- 
herent instability of the rock under 
changing temperatures. The break- 
ing of a hot glass plunged suddenly 
into cold water is a manifestation of 
the same force that in humid regions 
Effect of unequal heating of the surface to a Icsscr extent, in arid rcgions to 

a greater extent, tends to disrupt 
rock masses and to form soil. The 
temperature effects upon rock are 
of several kinds: (a) the breaking 
apart of large rocks into smaller 
masses through expansion and con- 
traction of the whole mass at an un- 
equal rate; (b) the peeling off of rock layers and chips from a rock surface 
or from the surfaces of bowlders through unequal expansion and contrac- 





Fig. I 

of a rock, (a) shows the condition of a block 
at uniform temperature ; {b) the manner in 
which the upper portion expands when heated 
above the average temperature; (c) the con- 
traction of the upper portion by cooling below 
the average temperature. When contraction 
and expansion are sufficiently great they result 
in the splitting of the surface layers. (Van 
Hise, U. S. Geol. Surv.) 



1 A. D. Hall, The Soil, 1907, p. 11. 



ORIGIN AND DIVERSITY OF SOILS 



15 



tion between the surface layer and the layer immediately beneath, a pro- 
cess known as exfoliation; and (c) temperature changes which expand 
different minerals at different rates and cause an internal strain to 
which the rock may finally yield. The first process (a) is so familiar 
as to require no description. The second process (b) may be understood 
by the recognition of the high temperatures which bare rock surfaces 
attain when exposed to the summer sun. On a hot day they may attain 
a temperature of 150° or 160°, a temperature so high that the hand 
can not be held on exposed surfaces without being burned. Between the 
highly heated surface particles and the particles some distance beneath 
the surface there must be a zone of shear, for at these high temperatures 
the surface rock will expand greatly, while the cool rock only a short 
distance beneath the surface is so much lower in temperature as to 
occupy smaller bulk, Fig. i. From observations made near Edin- 
burgh, Scotland, during 1841-42, the range of earth temperatures at 
varying depths in soil, sandstone, and trap rock was determined to be 
as follows: 

VARIATION OF TEMPERATURE WITH DEPTH ^ 



Depth 


Trap Rock 


Sand of Garden 


Craigleith Sandstone 


Max. 


Min. 


Range 


Max. 


Min. 


Range 


Max. 


Min. 


Range 


3 feet 

6 feet 

1 2 feet 

24 feet 


52.85° 
51-07 
49.00 
47-50 


38.88° 
40.78 
44-20 
46. 12 


13-97° 

10. 29 

4.80 

1-38 


54-50° 
52-95 
50.40 
48. 10 


37-85° 
39-55 
43-50 
46.10 


17-65° 

13-40 

6. 90 

2.00 


53-15° 
51-90 
50-30 
48-25 


38-25° 
38-95 
41.60 
44-35 


14.90° 

12-95 
8.70 
3-90 



Of course the surface inch or two or three inches show much greater 
ranges; and between the first and twelfth inches the differences may be 
extreme on hot summer days. The author has noted as the result 
of temperature observations on loose dry soil during several summer 
months a maximum difference of 35° to 50° between the first and fif- 
teenth inches, which was reduced to 5° or 10° before the following sunrise. 

Translating differences of temperature into units of expansion we have 
the rate of horizontal expansion varying from .000004825 inch per foot 
for each degree Fahrenheit in granite to .000009532 inch in sandstone.^ 
A change of temperature of 150° in a sheet of granite 100 feet in diameter 
would thus produce a lateral expansion of about i inch, an expansion 
that tends to lessen the cohesion of the rock and to cause a shearing of 

I Trans. Royal Society of Edinburgh, vol. i6, 1849. From G. P. Merrill, Rocks, Rock- 
weathering and Soils, 1897, p. 184. 

' W. H. Bartlett, Experiments on the Expansion and Contraction of Building Stones, etc. 
Amer. Jour. Sci., vol. 22, 1832, p. 136. 



1 6 FOREST PHYSIOGRAPHY 

the upper over the lower layers. Although these movements seem slight 
they are suflScient to produce in time a weakening and breaking of the 
rock, thus affording a better opportunity for the action of other physical 
and chemical agencies such as freezing water, bacteria, plant roots, etc.-^ 
This form of rock disintegration is most pronounced in massive coarse- 
grained rocks located in regions of great extremes of daily temperature 
such as occur in the arid and semiarid portions of the West. When it 
occurs in homogeneous massive rock it may produce rounded forms or 
bosses of very characteristic appearance. 

Stone Mountain, Georgia, 650 feet high, 2 miles long, and 1 1 miles wide, owes its elliptical 
dome-like form to such exfoliation along preexisting lines of weakness in the form of joints. 
The surface sheets are buckled up in very characteristic forms. They are rarely more than 
10 inches thick, but are 10 or 20 feet in diameter. In a few instances small avalanches have 
been caused by the giving way of such sheets. 2 

The third process (c) of rock disintegration through temperature 
change, that of crystal crowding, may be understood from the fact that in 
all rock composed of crystals there is an internal strain due to the unequal 
rates at which the component minerals expand upon increase of temper- 
ature. Such expansion has two forms of inequality: (a) the cubical 
expansion varies with the kind of mineral and (b) the rates along the 
various crystallographic axes of the constituent minerals are unequal.^ 

It is self-evident that a coarsely crystalline rock under these conditions will disintegrate 
more rapidly than a rock of finer grain. Rocks of granular structure, all other things being 
equal, undergo disintegration much more quickly than those in which the individual minerals 
are closely compacted, as a diabase or a quartzite. It is believed that dark-colored basic rocks 
tend to respond to the forces manifested by changes of temperature somewhat more readily 
than do light-colored acidic rocks, because of the more rapid absorption of heat by dark-colored 
objects in sunlight. It has also been shown that the thermal conductivity of rocks varies in 
direction according to the structure, being greatest in the direction of the schistosity, where this 
feature is developed. The result is that in massive, homogeneous rocks the conductivity is 
the same in all directions, while in finely fissile rocks it may be four times as great in the direc- 
tion of the fissility as at right angles thereto.* 

WIND AS AN AGENT IN SOIL FORMATION 

While the action of wind is most clearly seen on the surfaces of land 
waste where loose dry material may be shifted about in the form of 
dunes and sand drifts of variable size and shape, wind may also be an 
important agent in the actual production of soil. Loose particles of 
rock may be driven through the air against projecting rock ledges, and 
not only do they themselves tend to become finer through attrition in 

1 G. P. Merrill, Rocks, Rock-weathering and Soils, 1897, p. 181. 

2 Idem, pp. 245-246. 

3 G. P. Merrill, Stones for Building and Decoration, p. 419. 

* G. P. Merrill, Rocks, Rock-weathering and Soils, 1897, p. 184. 



ORIGIN AND DIVERSITY OF SOILS 17 

the air, but they also abrade obstructing ledges. This action takes place 
on a considerable scale in dry regions and may become one of the most 
important agents in the denudation of desert lands. ^ It has been 
estimated that the dust in a cubic mile of lower air during a dry storm 
weighs not less than 225 tons, while the amount of dust in the same 
volume of air during a severe storm may reach 126,000 tons.^ The great 
importance of the wind as a soil builder is shown by the wide distribu- 
tion of the loess deposits of the world. "It would perhaps be an ex- 
aggeration to say that every square mile of land surface contains 
particles of dust brought to it by the wind from every other square 
mile, but such a statement would probably involve much less exagger- 
ation than might at first be supposed."^ Dust transportation is not 
confined to desert regions, but takes place almost everywhere on some 
scale. 

Not the least important of the effects of wind on soil has been the 
wide distribution of volcanic dust as in Oregon, southern Idaho, etc. In 
the Tertiary period volcanic eruptions took place on a vast scale in many 
portions of the West. Great quantities of volcanic dust were raised 
aloft and then deposited at varying distances from the volcanic vents. 
In many instances such bodies of dust were swept by the wind hundreds 
of miles from their points of origin, and finally deposited as a sheet of 
loose waste. Since their original deposition the wind has played upon 
the surface layers, shifting them about, reworking and redepositing the 
material, and by these means modifying the qualities of the surface 
soil of many great tracts. 

BACTERIA 

Certain bacteria are able to draw their nourishment directly from the 
air in a purely mineral environment such as that found upon the surfaces 
of bare rock, so that even the denuded rocks of high mountains may 
be populated by these minute organisms. The ragged rocks of high 
altitudes and steep slopes in the Alps, the Pyrenees, the Vosges, etc., 
are composed of minerals of the most varied nature, all of which have 
been found to be coated with a "nitrifying ferment." These bacteria 
develop by absorbing carbonate of ammonia and vapors of alcohol from 
the air and they even assimilate carbon dioxide. The wide distribu- 
tion of these organisms, their great number, and the manner in which 

1 W. Cross, Wind Erosion in the Plateau Country, Bull. Geol. Soc. Am., vol. 19, 1908, 
PP- 53-62; S. Passarge, Die Kalahari, 1905; W. M. Davis, The Geographical Cycle in an Arid 
Climate, Jour. Geol., vol. 13, 1905, pp. 381-407. 

2 J. A. Udden, A Geological Romance, Pop. Sci. Mo., vol. 44, 1898, pp. 222-229. 
s Chamberlin and Salisbury, Geology, vol. i, 1904, p. 22. 



FOREST PHYSIOGRAPHY 




. 2. — Underground burrows and chambers of earthworm population, in well-drained sand bank near 
New Haven. The vertical burrows connect with underground chambers showing as dark lenses 
within an inch and an inch and a half of the bottom of the photograph. Seven or eight can easil}' 
be identified. At the time the photograph was taken many of the chambers and some of the burrows 
were completely filled with dark humus collected by the earthworms. When the humus was scraped 
away it was seen that each chamber had a smooth and generally fiat floor and an irregularly arched 
roof. Such of the openings as had been filled with humus had been abandoned. The open chambers 
and burrows were teeming with earthworms and with insects of many genera. The upper edge of 
the bank was broken down during a dry spell and at a time when the ground was fully stocked. The 
scale in the upper right hand corner is three inches long. (Photograph by Mason.) 



ORIGIN AND DIVERSITY OF SOILS 19 

they prepare the rock for the microscopic vegetation which is usually 
found in the form of a layer covering rock surfaces and soil par- 
ticles, place them among the important geologic agencies that have 
effected the disintegration of the rock and the formation of soils. ^ 

Their action is carried on on a small scale in cold temperatures and 
on a very large scale under normal temperatures where the rock is but 
thinly covered with earth. The action is also carried on among rock 
fragments, tending gradually to reduce them. The bacterial organisms 
penetrate every cleft or crevice, and by the chemical action of their 
secretions continually reduce the rock to smaller and smaller sizes, 
acting even on the most minute fragments. Each rock particle is found 
covered with a film of organic matter accumulated by these bacteria 
and the plants of a higher order which secure through them a food supply. 

ANIMALS AND HIGHER PLANTS AS SOIL MAKERS 

The most active animal agencies in producing and modifying soils 
are earthworms, which influence the physical state of soils by making 
them more porous and open. Darwin's studies showed that the intesti- 
nal content of worms has an acid reaction which has an effect on the 
soils passing through the alimentary canal. They still further modify 
soils by drawing into their holes leaves and other organic materials 
which gradually decay and are converted into humus, Fig. 2. Darwin 
estimated that an average of about 11 tons of organic matter is in 
this manner annually added to each acre of soil in regions where earth- 
worms abound. Earthworms tend also to increase the amount of 
ammonia in the soil, to make the soil finer by attrition during the process 
of digestion, and to mix the soil by bringing to the surface portions of 
the subsoil. They thus play a notable part in maintaining soil fer- 
tility. The excreta of earthworms contains more nitrogen and other 
easily oxidized compounds than the original soil, and after excretion by 
worms soil contains phosphoric acid and calcium carbonate in more 
readily soluble forms. ^ It has been observed that when earthworms 
are drowned out the surface soil layer remains compacted and vege- 
tation grows very feebly until earthworm immigration has restocked the 
soil.^ The action of burrowing animals, worms, insects, etc., in the soil, 
allows freer access of rain water and drainage water and increases the 
depth and the rate of rock and soil decay. Ants sometimes produce 

1 H. W. Wiley, Principles and Practice of Agri. Analysis: Soils, vol. i, 1906, pp. 39-40. 
- Cameron and Bell, Mineral Constituents of the Soil Solution, Bull. U. S. Bureau of Soils 
No. 30, igos, p. 41. 

3 A. D. Hall, The Soil, 1904, p. 159. 



20 FOREST PHYSIOGRAPHY 

highly important effects upon the soil, especially in tropical countries as 
in Brazil, where they often build tunnels hundreds of yards long which 
give the soil-making forces access to the subsoil. They carry great 
quantities of leaves into their nests and by this means and by their 
excreta contribute vegetable acids to the soil and thus promote rock and 
soil decay. ^ 

More general in their action upon both rock and soil are plants and 
plant roots. Roots force themselves into the crevices of rocks and 
minerals, they wedge apart rock masses, and thus expose new surfaces 
and a larger extent of surface to the action of other forces. The mechan- 
ical force exerted by growing roots is very great. The root of the garden 
pea has a wedging force equal to 200 or 300 pounds per square inch, a 
force that is exerted without harmful effects upon the small roots because 
of the protection afforded by the corky layer of the root tips.^ Vege- 
tation also assists in rock decay by shading the surface and permitting 
the retention of a larger amount of water upon the immediate surface 
where it exercises a dissolving action as already described. The organic 
matter contributed to the soil by decaying vegetation promotes rock 
decay by furnishing carbon dioxide or carbonic acid. Rootlets of plants 
in contact with limestone dissolve large portions of this rock through the 
solvent action of root moisture. The action of rock disintegration is 
also extensively carried on by the lower forms of vegetation, among 
which the lichens produce the most important effects. The rock sur- 
face is corroded and a soil cover originated. A prominent ingredient 
of the lichens is oxalic acid, an acid that compares in strength with 
hydrochloric and nitric acids, and that powerfully aids rock decay. 

Plant roots that permeate the soil are agencies of oxidation which 
have a very appreciable effect in altering some soil constituents and 
influencing soil fertility. Active extracellular oxidation is carried on 
by the plant roots chiefly by means of the enzymes (the name applied 
to any unorganized chemical ferment such as diastase, pepsin, etc.) 
which they excrete, and not to organic (carbonic acid alone excepted) 
and inorganic acids which they were formerly supposed to excrete. It 
is believed that the effect of the roots of growing plants in dissolving 
the organic substances of the soil is due chiefly to this action. Among 
phanerogams extracellular oxidation is strongly locahzed and limited to 
the absorbing surface of the root; the most intense oxidation is effected 
by the root hairs. Oxidation is more marked when an optimum water 

1 J. C. Branner, Ants as Geological Agents in the Tropics, Bull. Gaol. Soc. Am., vol. 7, 
i8g6, p. 25s; idem. Geologic Work of Ants in Tropical America, Bull. Geol. Soc. Am., vol. 21, 
1910, pp. 449-496. 

2 E. W. Hilgard, Soils, 1906, p. ig. 



ORIGIN AND DIVERSITY OF SOILS 21 

content is maintained in the soil, while saturation of the soil produces 
a decided depression in the rate of oxidation. Oxidation by plant roots 
is increased by the presence of calcium salts, potassium salts, phos- 
phates, nitrates, etc.^ 

The action of plants in promoting the formation of soil is well illus- 
trated by the manner in which plant associations succeed each other 
upon extensive areas of bare rock, a succession that is dependent upon 
the ability of each plant group to live under the hard conditions which 
exclude the next higher group, ^rustose lichens are the only plants 
which are able to establish themselves on a bare rock face. Upon 
the thin soil formed by these, other lichens are able to secure a foot- 
hold. Then appear the mosses, for example Hedwigia, Grimmia, etc., 
which eventually eliminate all but the erect (fructicose) lichens. The 
mosses still further increase the soil layer, both through the accumu- 
lation of mineral particles and by their own decay, and are in turn 
wholly or partly displaced by the more xerophytic species of ferns 
such as the spleenworts. With the ferns appear many herbaceous 
flowering plants, notably the stonecrops and saxifrages, and certain 
grasses. In addition to the carbonic acid which is excreted by the 
roots of all plants many of them secrete vegetable acids such as oxalic 
and citric acids which assist in soil formation. The herbaceous plants 
in turn prepare the way for, and are eventually succeeded by, shrubs 
and trees. 

Senft describes the vegetation that takes hold of landslips and coarse 
terrace deposits (near Eisenach) and shows how it undergoes great 
changes in type due to soil changes brought about chiefly by the vegeta- 
tion itself. In the locality examined the bare stony heaps were first 
clothed with mosses, then xerophytic grasses; later other xerophytic 
herbs came in and also shrubs like the juniper which gave rise to dense, 
bushy growths. In twelve years an impenetrable bush land had arisen 
and finally Sorbus, Fagus, and other trees appeared and a forest arose. 
During this change in vegetation type the soil had constantly changed 
and improved. Each kind of vegetation suppressed another — bush 
land vanquished xerophytic grasses, and forest vanquished bush land.- 

The effects of minor rock structures upon plants is extremely inter- 
esting. Peculiar and variable rock habitats induce variations in plant 
societies which are due chiefly to local differences in the nature of crev- 
ices — joints, fissures, etc. — in the rock. 

1 Schreiner and Reed, The Role of Oxidation in Soil Fertility, Bull. U. S. Bureau of Soils 
No. 56, 1907, pp. 7-9 et al. 

2 Quoted by Warming, (Ecology of Plants, 1909, Ox. ed., pp. 352-353. 



2 2 FOREST PHYSIOGRAPHY 

"Some of these receive water percolating from fiigher parts of the mountain, and may remain 
moist throughout prolonged periods of drought; other crevices obtain their water exclusively 
from the strictly local rain. Some crevices contain abundant detritus and are therefore endowed 
with a greater power of storing water; others are poor in detritus and allow the water to pass 
away. The chemical composition of the detritus also varies, as some crevices contain abundant 
humus, in which numerous earthworms may lurk, whereas others are poor in humus. Cracks 
in rocks supply an endless variety of habitats, each of which forms a special kind of environ- 
ment." 1 

The point is of exceptional importance in regions of thin soil where 
the lower roots of all plants and all the roots of some plants are in inti- 
mate association with the rock. Talus slopes frequently show similar 
variations. Their lower slopes or lower margins are commonly wooded 
because of the finer rock waste and the greater amount of water which 
here reappears. The loose upper slopes are treeless except where the 
talus has become temporarily stable and clogged with finer waste or 
where a change of geologic formation or the arrangement of crevices 
cause seepage, a common condition at the upper edge of talus slopes. 

The Causes of Soil Diversity 

The preceding discussion will enable us to see that the soil is an ex- 
tremely complex mixture. There are present mineral debris from rock 
degradation and decomposition; organic matter, the partly decom- 
posed remnants of former plant and animal tissues; the soil atmosphere, 
always richer in carbon dioxide and generally in water vapor than 
the atmosphere above the soil; living organisms, such as various kinds 
of bacteria, and often molds, ferments, and enzymes; and finally the 
soil water, a solution of products yielded by other substances. This 
enumeration is sufficient to show how diverse are the origins of the 
different components, and to suggest how varied are the reactions that 
take place in the soil even after its formation. These facts need emphasis 
because of the general view that soil is mere dirt or rock waste, or that 
it is everywhere the same, whereas the truth lies nearer the other extreme. 
The soil is a great complex of varied elements, formed in many ways, 
and subject to the most widely diverse changes after its formation. 
Nor have we exhausted the list of diversifying forces. We have yet to 
consider briefly the transportation of rock waste after formation, the 
various agencies concerned in it, and the results upon the soil texture 
and fertility. 

All soils are subject to some movement at the earth's surface, and 
since the soil particles are of different sizes, weights, and compositions, 
they must respond in different ways to the forces that tend to move 

1 E. Warming, (Ecology of Plants, Ox. ed., 1909, p. 245 



ORIGIN AND DIVERSITY OF SOILS 23 

them. The simplest case is that of deposition by running water, with 
gradually diminishing velocity, where on the whole the coarser particles 
are deposited first and the finer last. The action and the result are so 
familiar to all as to require no extended discussion. The distribution 
of material in an alluvial fan or a delta or a flood plain always follows 
this well-recognized law. The effects of creep and rainwash are not 
so simple. Under the influence of constantly changing temperature all 
hillside or colluvial soils tend to move down slope. Contributing toward 
the same result is the action of percolating soil water and ground water, 
cultivation, etc. In all these cases the fundamental and ultimate force 
is gravity, but because gravity is manifested in so large a number of 
forms it is clearer to consider the forms themselves and not the basic 
force on which they depend. In such cases of creep there is not that 
suspension of particles in water that permits thorough stratification 
or sorting, consequently coarse and fine are left mixed together, and the 
rate of movement may be so slow as scarcely to be perceptible. 

Where rock formations succeed each other in short distances soil creep 
may cause an important lack of sympathy between the underlying rock 
and the overlying soil. The soils of the higher may come to rest over 
the lower formations, and the rock character give little clue to the nature 
of the overlying soil. Cases of this kind are frequent in the Appalachian 
Mountains and the ridges of the Great Appalachian Valley, and are 
especially well marked where the boundary between two unlike forma- 
tions occurs on a hill slope. If the slopes are quite steep and the rock 
formations numerous on a given slope, such overplacement of soils may 
produce extreme effects and the waste from the different rocks become 
so mixed as to show at the foot of a slope or on the inner border of a 
foreland plain but little relation to any particular rock. On broad 
plateaus where the boundaries between rock formations are far apart 
mixtures of soil types take place to an important degree only near the 
boundaries of the formations; over the greater part of the outcrop of a 
given formation there is a close relation between the underlying rock and 
the soil. The Colorado Plateaus of the Southwest and portions of the 
Cumberland Plateau furnish excellent examples of this law. 

The rate of movement has been made the basis of a classification of 
soils according to origin that deserves a word of explanation. While all 
soils are subject to some movement, the movement may be so slow as 
to be of no importance, as on portions of flat tablelands or base-leveled 
areas like the Piedmont Plateau of Georgia and Maryland. Such cases 
of no movement or of little movement will tend to cause a certain sympa- 
thy between soil and rock in a given locality, and the minerals that occur 



24 FOREST PHYSIOGRAPHY 

in the rock are found in the soil or at least their decomposition prod- 
ucts are found there. Such soils are sedentary or residual soils, and 
the term generally imphes a fundamental relation between a rpck terrane 
and the soil covering it. On the other hand, if the soil has once been 
in the grip of a transporting agent such as the wind, running water in 
the form of river or brook, or a continental ice sheet, or a glacier, it is 
considered a transported soil; and the term transported always connotes 
a mixture of soil ingredients in the case of ice, and sorting in the case 
of water and wind. By these agencies soils may come to rest far from 
their place of origin. The alluvial deposits of the Mississippi flood 
plain are derived from fully one-fourth the whole United States. The 
underlying rock now perhaps deeply buried in a given locality may be 
limestone, but the alluvial soil overlying it may be deficient in lime and 
in still other ways less fundamental bear little or no relation to it because 
it was not derived from it to any important degree, or perhaps to any 
degree at all. No less true are these statements when applied to wind- 
borne soils. In every dry region whirlwinds raise aloft great clouds of 
dust that settle down near by or become more or less permanently lodged 
perhaps hundreds of miles away in extra-desert regions, where their 
relation to the rock or soil they overlie is purely fortuitous. The great 
loess deposits of western China, the dust soils of Oregon and Idaho, the 
loess deposits of the Mississippi Valley, all are illustrations of wind- 
borne soils, though they are not all fundamentally related to the extremes 
of arid conditions. 

Glacially transported material has or may have the same discordance 
with respect to the underlying rock. Over the sandstone and limestone 
areas of the Great Lake region has been swept glacial detritus in vast 
amounts, and although the material reflects the character of the under- 
lying rock to a notable degree (perhaps on the average about 80% of it 
is locally derived), yet an important share is also derived from northern 
locaHties. Bowlders of granite, gneiss, greenstone, slate, and basalt 
may be found scores and even hundreds of miles from their nearest out- 
crop, and everywhere in the glacial till are found important amounts 
of clay which were derived at least in small part from northern 
localities. The effects of the continental ice cap on the soil are discussed 
in greater detail in succeeding pages, and need not be further described 
here. Alpine glaciers have had less important effects upon soil because 
of their relatively slight development and because they have produced 
their effects chiefly in mountain valleys where their deposits are so 
restricted that though they may be important to the farmer they are 
relatively of less importance to the forester. 



ORIGIN AND DIVERSITY OF SOILS 



25 



The part that the various agencies concerned in soil formation have 
played in the making of the soil of North America is brought out in the 
following table. ^ 

DISTRIBUTION OF SOIL TYPES BY REGIONS 2 
(The surface of each continent is taken as 100) 



I. Alluvial regions: 

Loam predominating 

Mountain debris (gravel, etc.) 

Laterite (red ferruginous residual 
day characteristic of the tropics) . . 
II. Equality of destruction and transpor- 
tation 

III. Denudation preponderating: 

Eolian denudation 

Glacial denudation 

IV. Accumulation preponderating: 

Glacial accumulations 

Marine accumulations 

Stream and lake accumulations. . . . 

Shifting sand 

Fine eolian accumulations (steppe 
soils) 

Volcanic accumulations 

V. Dissected loess deposits 

VI. Coral Islands 



Total . 






IS 



16 



^1 



25 



^^3. 



The kinds of residual soil that result from the decomposition of the 
various kinds of rock at the earth's surface are both numerous and vari- 
able. For a number of typical illustrations the student is referred to 
the convenient tables from Merrill in Appendix B. These tables present 
in summary fashion the chief facts with which he should be acquainted. 
They may well be supplemented by readings in Merrill'' and Pirsson,'' and 
by the chapter on Land Waste by Davis.^ In the interpretation of these 
data it is well to bear in mind that not always is the rock character re- 
vealed in the soil character even in the case of residual soils. Limestone 
soils usually contain adequate amounts of lime, but sometimes they are 
so deficient in this respect that artificial liming is one of the chief neces- 

1 Compiled by A. von Tillo from Sheet 4 of Berghaus' Physikalischer Atlas and from Richt- 
hofen's Fiihrer fiir Forschungsreisende, p. 498. Original table occurs in Die Geographische 
Verteilung von Grund und Boden, Petr. Mittheil., vol. 39, 1893, pp. 17-19. 

2 Translation from von Tillo with modifications. 

3 Rocks, Rock-weathering and Soils, 1896. 
* Rocks and Rock-making Minerals, 1909. 
6 Physical Geography, 1899, pp. 263-296. 



26 FOREST PHYSIOGRAPHY 

sities to bring them up to normal fertility. Likewise the soil resulting 
from the decay of rocks such as certain basalts of Idaho that contain 
a great deal of apatite (phosphate of lime), a mineral which generally 
yields phosphoric acid to the soil, may hold the phosphorus in an in- 
soluble form and make the addition of this ingredient one of the first 
necessities. To some extent also the geologic history of a region is im- 
portant in the interpretation of the soils, for a cherty dolomite overlying 
a shale may yield its insoluble elements to the shale surface long after 
the soluble part of the dolomite has been removed. Some regions have 
been dry that now are moist, some moist that now are dry, and each 
change has effected a change in the soil. Many similar geologic inherit- 
ances are known that produce soil effects of fundamental importance. 



CHAPTER II 

PHYSICAL FEATURES OF SOILS 
Size and Weight or Soil Particles 

We have now seen that the soil is a complex mixture of mineral par- 
ticles, soluble and insoluble chemical substances, gases, liquids, living 
organisms and dead organic matter, various kinds of bacteria, and 
often molds and enzymes. But the chief ingredients of most soils and 
important ingredients in all soils are the mineral particles originally 
derived from rock. A soil may be so coarse that it consists of little 
more than huge stones and bowlders with which are intermingled small 
quantities of rock fragments; or it may be so fine that, as in the case of 
the finest clays, the diameter of the individual particles is only one- 
thousandth of a millimeter. A pound of such material would be com- 
posed of grains whose aggregate surface extent would be 110,538 square 
feet, or more than 2h acres. The number of grains in a gram of soil 
of such fineness would be 720,000 billion. In ordinary soils the num- 
ber of grains in a single gram varies from about 2 to about 5 million.^ 

The average specific gravity of soils with an ordinary amount of 
humus will range between 2.55 and 2.75. The lightest constituent is 
kaolinite, 2.60, and the heaviest are mineral particles containing much 
iron such as mica and hornblende, which may range over 3.00. The 
specific gravity is, however, of less importance than the volume weight, 
or the weight of the natural soil in terms of an equal volume of water. 
A cubic foot of water weighs 62^ pounds, while the average weight of 
an equal volume of soil is about 75 or 80 pounds. The extremes are 
represented by calcareous sand, no, and peaty and swampy soils, 30.^ 
It is important to see at once that what are known as light and heavy 
soils in agriculture and forestry are not light and heavy in terms of 
either gravity or volume weight but in terms of tillage and root penetra- 
tion. Clay is a light soil (70-75 pounds) as to volume weight; pure or 
moderately pure clay soils are among the heaviest known to agriculture. 
In general the greater the amount of humus in the soil the lighter it is.^ 

1 Milton Whitney, Bull. U. S. Weath. Bur., No. 4; F. H. King, Physics of Agriculture, 
p. 117. 

2 E. W. Hilgard, Soils, 1907, p. 107. 

' For standard methods of determining the specific gravity of soil see H. W. Wiley, Prin. 
and Prac. of Agri. Anal., vol. i, 1906, pp. 96-97. 

27 



28 



FOREST PHYSIOGRAPHY 

Pore Space and Tilth 



The physical organization of the soil is extremely varied from place 
to place. Certain sandstones are composed of grains of very uniform 
size, and weather into a soil of unusually uniform texture. The relations 







Fig. 3. — Diagram to illustrate pore space in soils 

of the individual grains of such a case are represented in Fig. 3 B, where 
a high percentage of pore space is afforded. If, however, the grains vary 
in size, the smaller will occupy the interstices between the larger, the 




Fig. 4. — The most compact packing of a mass of spheres (left), and unit element of the pore space in 
such a mass (right). (Slichter, U. S. Geol. Surv.) 

volume weight will be increased and the pore space will be diminished, 
Fig. 3 C. The extent of the pore space may be determined by finding 
the difference between the specific gravity and the volume weight of 
the soil. For soils composed of particles of uniform sizes the smaller 



PHYSICAL FEATURES OF SOILS 29 

the size of the grain the smaller the unit pore space, the larger the size of 
the grain the larger the unit pore space; under all circumstances the 
amount of pore space is decreased by increase of variability in the size 
of the individual particles. The value of the porosity is independent of 
the size of the grains where these are uniform in a given mass; it is de- 
pendent merely upon the manner of packing. The minimum porosity 
of a mass of uniform spheres is 25.95% o^ the whole mass occupied by 
them, Fig. 4; the maximum porosity is 47.64% of the whole space. ^ The 
pore space in most cultivated soils ranges from 35% to 50%, and theo- 
retically may be as high as 74.05%, if the soil is flocculated and the 
floccules or crumbs arranged as in Fig. 3 D ; in sandy soils it may be 
only 20%. 

The actual field condition of a soil as to pore space will depend upon 
the rainfall, methods of tillage, types of vegetal growths, and the 
chemical composition of the soil particles. Cultivation results in the 
formation of soil crumbs or soil aggregates which give the soil a loose 
condition known as tilth. The volume weight is decreased and the 
pore space increased by this condition. Wollny- estimates that the 
increase of soil volume through such flocculation may amount in the case 
of consolidated clay to as much as 41.9%; on moistening, dry clay 
increases in bulk 30% to 40%. Flocculation may be caused by lime 
carbonate, and to the action of this substance are due the easy tillage 
of limestone soils and the loose condition of the loess deposits of the 
western part of the country. The aggregates may range in size from 
10 or more inches to those of microscopic size. The steep bluffs char- 
acteristic of loess are explained by the gripping together of the rough 
soil aggregates which compose the loess. The most common cem.ent 
that aids crumb structure or soil flocculation is clay, and the action is 
one of the most important attributed to this soil substance. The fresh 
colloidal humates of lime, magnesia, and iron act in the same manner, 
while silica, silicates, and ferric hydrates have the same action but to 
a less important extent. Tilth is maintained in nature by humus 
(one of its most important functions) and by root penetration, while 
the deflocculating action of beating rains is prevented in nature by a 
cover of forest litter or of grass and herbage. Saturated soils have many 
defects, such as a high percentage of acids, lack of aeration, etc., but 
one of their chief defects is the absence of crumb structure, the compact 
subsoil to which this leads, and the difficulty of root penetration. 

1 C. S. Slichter, The Motions of Underground Waters, Water-Supply Paper U. S. Geol. 
Surv. No. 67, 1902, p. 20. 

* Quoted by E. W. Hilgard, Soils, 1907, p. no. 



30 FOREST PHYSIOGRAPHY 

Special Action of Clay 

When soils contain too much clay they may act almost like pure clay 
and, like certain of the prairie soils of the western part of the United 
States, develop wide cracks during the dry summer months. This 
action has been described as contributing greatly to the drying out of 
the soil to some depth, the mechanical tearing of the delicate roots, 
and sometimes the total destruction of vegetation. In some clay soils 
the shrinkage after rain or irrigation is sufficient to cause the surface 
crust to contract about the stem and so injure the bark as to interfere 
with the proper growth of the plant. ^ The amount of shrinkage in 
the case of heavy clay soils has been measured; it ranges from 28% to 
40% of the original volume. When the content of colloidal clay falls 
below 15% the shrinkage in drying is so slight as to produce no damage, 
and in sandy soils no perceptible volume change occurs. In the case of 
certain alkali soils of California the alkaline carbonates prevent floc- 
culation and render tillage difficult or impossible, a result that is effec- 
tively offset by the use of gypsum. Such action is not, however, wholly 
destructive, for the falling into the cracks of the surface material at the 
next wetting causes a sort of inversion of the soil, to which is thought 
to be due in part the long duration of fertility in the case of many 
clay soils. 

Soil and Subsoil 

No sharp distinction has yet been generally accepted between soil 
and subsoil. A change in color from the darker surface layer (due to 
the presence of humus or ferric hydrate) to the lighter subsurface layer 
is the usual basis of the distinction, but this breaks down in the arid 
region where humus is either present in very small quantities or is wholly 
absent. Some would base the distinction upon change from rock to 
rock debris, and while this works well in the case of a shallow cover of 
land waste it is unsatisfactory in the coastal plains of the world and in 
a number of other types of places where the loose material of geologi- 
cally recent deposition may reach down hundreds of feet. The color 
and humus distinctions harmonize with a number of other qualities, 
such as absence of structure, in setting off the surface layer of a few inches 
to a few feet as the soil and the material below that as the subsoil, and 
we shall regard this distinction as the most valid and acceptable. 

Among the distinctions noted between soil and subsoil one of the 
most important is the humus content. The depth to which humus is 
found varies somewhat with the nature of the plant growth and is often 

1 E. W. Hilgard, Soils, 1907, p. 112. 



PHYSICAL FEATURES OF SOILS 3 1 

found to extend in notable quantities to the lower limit of development 
of the roots of annual plants. Variation in the root habit of different 
kinds of plants therefore brings about a variation in the depth of the 
soil as determined by the humus content. Fertilization tends to change 
the structure, chemical composition, and degree of compactness. In 
swamps and marshes the humus tint may reach to such depth as to in- 
validate the distinctions based upon humus content. 

Since humus is porous and has a high water-absorbing and water- 
holding capacity, and since the surface layer of soil may consist of 
much finer particles than the subsoil, it is clear that the water content 
of soil and subsoil may be very unlike, both in time of drought and in 
time of abundant rain. Aeration is also more nearly perfect in the 
surface soil than in the subsoil and perpetually continues many chemical 
processes of great importance in transforming soil substances into avail- 
able plant food. 

Further differences between soil and subsoil deserve consideration. 
As a rule the subsoil is more clayey than the surface soil, hence subsoils 
of residual origin are generally less pervious and more retentive of 
moisture and plant foods in solution than the surface soil. Since the 
finest particles of soil are usually those richest in plant foods, subsoils 
as a rule would tend to accumulate larger potential supplies of plant 
food than the surface soil. These results are due to the penetration 
of the soil by rain water, which carries the finer particles down with it 
into the subsoil. The steady depletion of the surface soil in the humid 
regions by downward percolation would tend to produce far-reaching 
contrasts between soil and subsoil were it not for the fact that between 
rains evaporation progresses steadily and capillary action tends constantly 
to bring soluble salts nearer the surface, where they are deposited through 
evaporation of the water in which they are held, thus periodically in- 
creasing the amount of available plant food in the surface soil. The 
process is always beneficial in a humid region, but in an arid region 
may result in so large a surface accumulation of salts (p. 97) as to 
be injurious to plant growth. 

Subsoil is usually more calcareous than the overlying surface soil, 
and this difference is so marked in some cases that the surface soil 
requires lime replacement when the subsoil contains a relatively large 
amount of lime carbonate. It may accumulate to such an extent as 
to form a solid subsoil mass or hardpan. It is noteworthy that the 
minerals of the subsoil are in a less weathered condition than those of 
the surface soil — a condition due largely to the absence of humus and 
associated carbonic and other acids, so that the subsoil is often spoken 



32 FOREST PHYSIOGRAPHY 

of as ''raw." In arid regions the characteristic differences between soil 
and subsoil as developed in humid regions disappear to a large extent. 
The slight percolation of water does not greatly favor the accumulation 
of fine colloidal clay in the subsoil, so that both soil and subsoil are of 
the sandy type and air penetrates to a great distance. Extreme figures 
for aeration in arid subsoils are a few hundred to a thousand feet, as 
shown by oxidation of ore in rock to that depth. The distinction be- 
tween soil and subsoil in humid regions as based on the humus content 
likewise disappears in arid regions partly because the amount of vege- 
table matter contributed to the soil is so small, partly because oxidation 
is so active that vegetation is in some cases completely "burnt up "and 
is not incorporated in the soil, and partly because the long roots of arid 
region plants are widely distributed through the deeper layers and 
largely absent from the surface layer. 

The porosity of arid soils and subsoils and their dryness result in 
an extraordinary root penetration in trees, shrubs, and taproot herbs 
whose fibrous feeding roots are found deep in the subsoil and some- 
times wholly absent from the surface soil. The roots of grapevines 
have been found 22 feet below the surface, and in the loess of Nebraska 
the roots of the native Shepherdia have been found at a depth of 50 feet. 
It is quite otherwise in the case of humid soils. The greater fertility 
of the surface layer and the abundance of air and other desirable sub- 
stances, including humus, result in a great development of small feeding 
roots at the surface, where the largest and most active portion of the 
root system is found; while the water supply is derived either through 
a long taproot or through deeply penetrating water roots having the 
same function, or the whole root system of the plant has been modified 
to suit moist surface or subsoil conditions. 

Sometimes the geologic mode of origin of the land waste of a locality 
is responsible for an extremely coarse subsoil overlain by thin layers of 
fine wind-blown or stream-deposited material. The coarseness of the 
subsoil of such a locality tends not only to depress the water table (p. 44) 
but also to repress capillary action. The result is often disastrous to 
all but the most deep-rooted vegetation. Indeed some localities exhibit 
extreme conditions; the subsoil may be almost perfectly dry during 
a dry season, while the surface soil is perceptibly moist and supports 
growing plants. This condition is seen on many outwash plains of the 
glaciated region and is one of the most serious drawbacks in the develop- 
ment of agriculture on the outwash plains of Long Island, as well as in 
the larger valleys of the arid region. The possibility of the condition 
should always be borne in mind, for it is always a reasonable expectation 



PHYSICAL FEATURES OF SOILS 33 

in transported and water-laid soils. This class of soils may offer con- 
ditions of soil and subsoil quite unlike those outlined above. When they 
are of recent origin almost any contrast between soil and subsoil may 
occur. The wandering of a waste-laden stream over an aggrading flood 
plain may bring about a covering of fine silt over clay or gravel; on the 
other hand the same stream in a near-by locality may cause the formation 
of clayey deposits where it formerly deposited the coarsest material. 
On the seaward margin of a coastal plain it is also common to find wide 
variations between soil and subsoil, but the variations are not always 
of the same kind or to the same degree, and will depend to some extent 
upon the shore conditions at the time of deposition of the coastal plain 
sediments of a given locality, and to a great extent upon the drainage 
conditions and degree of dissection since uplift of the coastal plain. 

Soil Air 

Plants may be drowned through lack of free oxygen when their roots 
are submerged. Besides this harmful effect of submersion is the lack 
of continued oxidation of the soil particles and the formation of plant 
foods. Furthermore, nitrification ceases and denitrification sets in. 
Aeration is therefore an essential process for the best plant growth, and 
by this is meant the admission of air not merely into the surface layers 
but deeply into the root zone so that the decaying organic matter in 
the form of roots and leaves carried down by earthworms may be formed 
into nitrogen by the carrying forward of the nitrifying process, which is 
dependent upon a supply of oxygen. In addition it should be noted 
that many purely chemical reactions essential to soil fertility require a 
certain amount of oxygen and carbon dioxide for their continuance. 

The amount of air space in soils is from 35% to 50% of their 
volume, and when soils are in their best condition for the support of 
vegetation about one-half of this space is filled with water, the other 
half with air. A number of investigators agree in assigning to unculti- 
vated forest soil only about half as much air per acre foot as in the case of 
a well-cultivated garden soil, or from 4000 to 6000 cubic feet. The. com- 
position of soil air is different from that of the atmosphere in that soil 
air usually contains a larger amount of water vapor, a higher nitrogen 
content, a lower oxygen content, a larger amount of carbon dioxide, etc. 

One of the chief objects in draining a soil is to facilitate aeration. 
For while soil water is composed in part of oxygen it is not in a free state 
and requires chemical alteration to be suitable for the transformations 
in which oxygen plays a part. The various bad effects of lack of aeration 
are, chiefly, a stoppage of the important process of nitrification, the but 



34 FOREST PHYSIOGRAPHY 

partial decomposition of organic matter in the soil, a drowning out of 
earthworms, insects, etc., whose effects in maintaining soil fertiUty are 
important, and a reduction of the soil temperature. Aeration denotes 
good drainage; lack of aeration poor drainage, except in the case of 
stiff clay, where air may be excluded to a certain extent even when the 
clay is relatively dry. Clay soils are in general poorly aerated because 
their fineness of texture causes a large area of grain surface and this in 
turn a large water- retaining capacity. On certain areas of the Oxford 
clay and London clay of England the pastures degenerate in a few years 
into masses of creeping plants and the land must be cultivated afresh 
in order to aerate it. The clays are so fine-textured that they become 
water-logged when allowed to stand without cultivation. In order to 
aerate the soil the Dutch farmer of the lowlands causes the water table 
to sink to a depth of a meter during autumn and winter, but during the 
remaining months only to a depth of a half-meter; and a similar practice 
is followed in certain meadows in Denmark. A wet, badly aerated 
soil, poor in oxygen, obstructs plant respiration and represses the func- 
tional activity of the roots. 

The amount of air in the soil affects the internal structure of the plant 
so that in very wet soil the plants that thrive frequently have very large 
internal air spaces which are in communication with one another through- 
out the whole plant and can even convey air from the atmosphere itself 
to the most distant root tips and parts of the rhizomes.^ 

Loam, Silt, and Clay 

Loam, silt, and clay are of exceptional importance in the soil. The fine- 
ness of their constituents causes notable effects upon the water content 
of soils, upon the solubility of the soil substances, and upon the facility 
of root penetration, so that it may be taken as a general principle that 
the fine material of a soil has an importance quite out of proportion to 
its relative volume or volume weight, and the determination of its exist- 
ence and amount are of the greatest importance in a mechanical analysis 
of the soil. 

LOAM 

The term " loam " is perhaps one of the most indefinite words in the 
vocabulary of the layman who undertakes to speak about soils. It is 
used in a very loose and sometimes wholly indefinite way even by some 
soil physicists and it is therefore necessary to note its features in a special 
manner. From the table on p. 722 it is easy to derive the empirical 
formula for loam. As there defined it is a soil that contains less 

> E. Warming, Oicology of Plants, Ox. ed., 1909, p. 44. 



PHYSICAL FEATURES OF SOILS 35 

than 55% of silt and more than 50% of silt and clay; but the 
essentials of that formula are not brought out by its mere statement. 
The essential feature of a loam is that it is a mixture in certain propor- 
tions of fine with less fine material. That mixture may represent the 
widest extremes of soil material, such as stones and bowlders mixed with 
silt and clay in right proportions, and would then be called a stony loam; 
or it may be either a coarse or fine or medium sand that is mixed with 
clay or silt or a mixture of these two substances, in which case it would 
be called a sandy loam. Loam is therefore not to be thought of as a certain 
soil ingredient such as sand or silt or stones, hut as a condition of mixture 
which makes it desirable to designate the mixture and not the individual 
components and to express such designation by a specific name. This 
explanation can not be stated too emphatically, because a great many 
writers loosely consider a soil to be a loam when "loam" predominates, 
and call it a sandy loam if a certain important amount of sand occurs in 
the soil. If on the other hand the sand predominates they call the sam- 
ple a sandy loam instead of a loamy sand. Such a designation makes 
the erroneous assumption that "loam" is a substance instead of a 
condition of mixture. It is scarcely necessary to add that humus 
added to clay or sand or silt in right proportions makes a loam or that 
clay added to gravel in certain proportions makes a loam, etc. 

SILT 

The term " silt " is commonly employed to denote the finest material 
of the soil above clay. In the mechanical analysis of soils only differences 
in size of grain are determined and it might therefore be assumed that 
silt resembles sand in chemical constitution. They are on the contrary 
unlike in their chemical nature but the differences are not radical. In 
sand, quartz is the principal mineral; in silt the hydroxides and hy- 
drous silicates predominate. Neither product is wholly free from the 
other and neither is uniform in character since the character of the sedi- 
ments everywhere reflects to some degree the character of the rock 
from which the sediments were derived. In regions of basic rock, for 
example, the sediments are rich in iron; in granite regions the sediments 
are composed largely of aluminous residues.^ 

^> CLAY 

Residual clays originate through the decomposition of crystalline 
rocks. They are pure or of high grade when they are derived from rocks 
which contain only silicates of alumina or when the movement of the 

1 F. W. Clarke, The Data of Geochemistry, Bull. U. S. Geol. Surv. No. 330, 1908, p. 428. 



36 FOREST PHYSIOGRAPHY 

ground water is thorough enough to remove other more soluble salts 
as fast as formed. Since these conditions are rarely fulfilled it follows 
that even the purest deposits of clay usually contain crystals of quartz 
and other types of resistant minerals. The acids of ground water have 
far less effect upon aluminum than upon the other bases, so that the 
greater part of this base remains in the soil and collects in such amounts 
as to form deposits containing large percentages of clay (silicate of 
aluminum) or kaolin. 

" Clays may be defined as mixtures of minerals of which the representative members are 
silicates of aluminum, iron, the alkalies, and the alkaline earths. The hydrated aluminum 
silicate, kaolin (Al2O3.2SiO2.2H2O), is the most characteristic of these. Some feldspar is 
usually present. The grains of these minerals may show crystal faces (especially in the case 
of kaolins), but more commonly they are of irregular shapes. Upon most of these grains is 
an enveloping colloid coating. This is mainly of siHcate constitution, but may consist partly 
of organic colloids, of iron, manganese, and aluminum hydroxides, and of hydrated siHcic acid. 
Quartz grains, which are generally present, and mica, which is frequently present, do not have 
the colloid coating or have it in much less degree. Almost any mineral may be present in 
clays and modify the properties somewhat. The combination of granular materials and colloids 
is in such proportion that, when reduced to sufficiently fine size (by crushing, sifting, washing, 
or other means) and properly moistened with an appropriate amount of water, plasticity is 
developed. If the colloid matter is in excess the clay is considered very plastic, fat, or sticky, 
but if the granular matter is in excess it is called sandy, weak, or nonplastic. " ' 

Transported clays owe their existence to the sorting action of water. 
The deposition of the transported material according to size leaves the 
fine clay to be deposited last. Hence clay deposits may be found on 
lowlands where more or less regular inundations permit of the subsid- 
ence of clay as the end of a series of quiet water depositions in back 
swamps and flood plains. Clay may also be formed as a marine or 
lacustrine deposit to become dry land either through the elevation of 
the deposits by crustal movement or through the draining of a lake or 
partial draining by the cutting down of the outlet, the silting up of the 
lake floor, the tilting of the land, or the growth of shore vegetation. 
The formation of pure clay can take place only under exceptional con- 
ditions, since deposition is usually in the form of floccules of coarser 
material which carry down the finer particles with them even when the 
water is undisturbed. 

COLLOID CLAY 

The name "colloid" (resembling glue or jelly) is applied to the clay 
particles that remain suspended in water for 24 hours or longer. The 
presence of an electrolyte such as a soluble salt causes the discharge of 
the static electrical charges either positive or negative to which the 
suspension is thought to be due and the subsidence of the colloid follows. 

1 H. E. Ashley, The Colloid Matter of Clay and its Measurement, Bull. U. S. Geol. Surv. 
No. 388, 1909, p. 7. 



PHYSICAL FEATURES OF SOILS 37 

This explains the hastened subsidence of colloidal matter in river water 
when it is discharged into a salty sea. Besides the true clay of the 
extremely fine substance of soils there are present, usually in all soils, 
substances such as silicic, aluminic, and zeolitic hydrates, which are all 
nonplastic and yet fine enough to form part of the clay substance as 
usually described.^ The plasticity appears to be due solely to those 
particles of the clay substance which do not settle in the course of 24 
hours through a column of pure water 8 inches high. Colloid clay is a 
jelly-like substance which shrinks greatly on drying and when dry ap- 
pears like glue. It adheres to the tongue with great tenacity, swells 
rapidly when wetted, and is highly adhesive and plastic. It may also 
be separated from water by evaporation of the water or by the use of 
lime which flocculates the clay particles and causes them to subside. ^ 

CLASSIFICATION OF CLAYS 

Clays are designated according to the predominance of certain con- 
stituents: some are calcareous and are called marls; some contain a great 
deal of fine quartz and are known as siliceous clays; while others are 
rich in iron oxides and are called ferruginous clays or ochers, etc.'^ The 
brickmaker, the ceramist, and others have refined classifications based 
upon the special qualities clays exhibit when used for special purposes 
and under special conditions. These are, however, not natural features 
of clay in the soil and therefore lie outside our field of study. 

Of all the mineral constituents of the soil clay is without doubt the 
most important because of its peculiar role in the physical structure of 
the soil, whereby it affects root penetration, drainage, fertility, etc. Its 
fineness and plasticity cause it to fill the soil spaces to the degree to 
which it is present and to cause the soil particles to adhere and to form 
soil crumbs, or floccules, which in turn results in a more open structure 
and therefore better aeration, better drainage, more rapid humification 
of organic matter, etc. Without clay, sand flocculates only when moist; 
when thoroughly wet or thoroughly dry the particles collapse and the 
soil assumes a single grain structure instead of a crumb structure. The 
whole soil mass then becomes densely packed and its fertility reduced 

1 H. W. Wiley, Prin. and Prac. of Agri. Anal: The Soil, 1906, p. 182; and E. W. Hilgard, 
Soils. 1Q07, 59-85. 

- For further data concerning the various theories of plasticity and the composition of 
clays see the following references: 

Th. Schloesing, The Constitution of the Clays, Compt. Rend., vol. 79, 1874, pp. 386-390, 
473-477- 

A. S. Cushman, The Colloid Theory of Plasticity, Trans. Am. Ceram. Soc, vol. 6, 
pp. 65-78. 

' L. V. Pirsson, Rocks and Rock-forming Minerals, 1909, p. 281. 



38 FOREST PHYSIOGRAPHY 

both because of the exclusion of adequate amounts of water and because 
roots are not able to penetrate it. The compacting is furthered by the 
presence of grains of many sizes in somewhat equal proportions; under 
these circumstances the smaller grains fit into the interstices of the 
larger and give the soil an imperviousness that makes it very diflScult 
of cultivation. The same result may be achieved in a soil with a high 
percentage of fine sediments and an equally high percentage of large 
grains. This combination in the absence of either intermediate grains 
or clay will effect a high degree of impermeability. The comparable 
influence of forest litter, humus, etc., on soil tilth, is discussed in 
Chapter VI and will not be treated here. 

It is to the tendency of clay to bind the particles of the soil and 
give it tilth or open texture that the loaminess of soils is due when 
their chief constituent is sand. The small percentage of clay required 
to produce important effects is shown in the following table,^ but 
in interpreting it the reader should keep in mind that by clay is meant 
the colloidal clay as noted above and not alone the fine substance 
separated by elutriation and of different character both physically and 
chemically from a colloid. 

Very sandy soils . 5% to 3% clay 

Ordinary sandy lands 3 . 0% to 10% clay 

Sandy loams 10.0% to 15% clay 

Clay loams iS-o% to 25% clay 

Clay soils. 25.0% to 35% clay 

Heavy clay soils 35 -0% to 45% and over 

Like humus, clay is very retentive of water and soil gases as well as 
of solids dissolved in water, qualities so markedly absent in certain 
coarse soils as to render them almost useless for agriculture in spite of 
the presence of a rather large amount of plant food as shown on chemi- 
cal analysis. Furthermore the clay substance in the soil while it itself 
contains nothing of value to the plant (silicate of aluminum in its pure 
state being of no importance whatever in nutrition) yet contains within 
its mass in a fine, easily dissolved, and highly decomposed condition 
other soil minerals or substances of great importance. Among the 
most important of these are potash, lime, soda, etc. As an illustration 
of the origin of such substances may be mentioned the soda-lime and 
potash feldspars. Those containing lime are more readily attacked 
than those containing potash. All clays arise from the decomposition 
of the feldspars, augite, hornblende, etc., and as these minerals all gen- 

1 According to E. W. Hilgard, Soils, 1907, p. 84. 



PHYSICAL FEATURES OF SOILS 



39 



erally contain potash the clays are the source of the available potash in 
the soil; therefore the amount of potash in the soil usually varies with 
the amount of clay.^ In many cases also zeolitic compounds are associ- 
ated with clay. These are hydrous silicates of lime or alumina which 
in the presence of a solution containing a stronger base such as potash 
or soda may yield the displaced base to the soil as a soluble substance 
of great potential value to plants. - 

The insolubility of clay, suggested by the fact that it is an ultimate 
product of rock decomposition, is one of its chief defects, though the 
defect is generally not apparent in nature because clay has a strong 
affinity for many soluble salts of great importance as plant food. The 
manner in which the soluble material of a soil rapidly increases with 
increase in fineness and the importance of clay in this respect are 
well brought out in the following table modified from the table by 
R. H. Loughridge.^ 



RELATION OF SOLUBLE MATTER TO SOIL CLASS 



Conventional Name 



Clay Finest Silt Fine Silt 



Medium 
Silt 



Coarse Silt 



Per Cent in Soil 



Diameter of Particles 



Constituents 



21.64% 



Insoluble residue 

Soluble silica 

Potash (K2O) 

Soda (NasO) 

Lime (CaO) 

Magnesia (MgO) 

Manganese (Mn02) 

Iron sesquioxide (FeoOg) . , 

Alumina (AI2O3) 

Phosphoric acid (P2O6) . . . 

Sulphuric acid (SO3) 

Volatile matter 

Totals 

Total soluble constituents 



15.96 

33- 10 
1.47 

(1.70) 
0.09 
1-33 
0.30 

18.76 



0.06 
9.00 



100. 14 
75-18 



23.56% 



mm. 
.005-. 01 1 



73-17 
9-95 
0.53 
o. 24 
0.13 
0.46 
0.00 
4.76 
4-32 

O. II 

0.02 

5.61 



99-30 
20.52 



12.54% 



mm. 
.013-.016 



87.96 
4.27 
o. 29 
0.28 
0.18 
0,26 
o. 00 

2-34 
2. 64 
0.03 
0.03 
1.72 



100.00 
10.32 



13.67% 



mm. 
.022-.027 



94-13 
2-35 



-03 
.92 



100. 21 
5-16 



13-11% 



mm. 
-033-.038 



96.52 



The table shows that clay contains about 33% of soluble silica, finest 
silt about 10%, and medium silt about 23^%. The total soluble in- 



1 A. D. Hall, The Soil, 1907, p, 19. 

2 On the Distribution of Soil Ingredients among the Sediments obtained in Silt Analysis, 
Am. Jour. Sci, vol. 7, 1874, p. 18. Analysis based on a yellow loam from Mississippi. Desig- 
nations of soil classes do not follow present conventions. 



40 FOREST PHYSIOGRAPHY 

gredients in the same order are 75%, 203^2%; and 5%. The clay is by 
far the richest in mineral ingredients, the amount being more than 
twice as great as that contained by all the other soil substances com- 
bined. Its insoluble residue is very small, its volatile matter is the 
largest, it contains more soda and manganese, and it heads the list in 
the amount of free silica it contains. The availability of the soluble 
material, however, depends on the tilth and the water supply to a large 
degree, and a fine soil must have a proportionately greater water supply 
than a coarse one or its otherwise more favorable qualities will be 
counterbalanced by excessively slow transference of plant food. 



CHAPTER III 

WATER SUPPLY OF SOILS 

Relation to Plant Growth and Distribution 

Water is of fundamental importance in ecology. It constitutes from 
65% to over 95% of the tissues of plants, is a necessary part of all cell 
walls and of protoplasm, is vital to all transference of plant food and 
even to the forming of plant food in the soil, is the agent of respiration, 
in general is the factor that most frequently conditions life and death, 
and hence has a predominating influence upon both the internal and 
external structures of the plant. ^ Not only does the rainfall determine 
the great regional types of vegetation ; it determines also the finer shades 
of detailed distribution where topographic differences occasion great 
variability in the rainfall distribution from point to point. It is of even 
more importance than heat, for it is of more irregular distribution. 
Its importance is reflected in a number of indirect ways as well as in 
the more familiar direct ways. For example, a windy region is likely 
■to be a dry region for plants, and if not dry in a physical sense is almost 
bound to be dry in a physiological sense.- Wind dries the soil and in- 
creases transpiration in the plant to such a degree that places most 
exposed to it have a relatively xerophilous vegetation. The eastern 
protected hill slopes of central Jutland are clothed with forest; the 
western exposed hill slopes are covered with heath. On the northern 
border of the subarctic forest, bands of trees extend down the sheltered 
valleys far beyond the continental timber line. The most remarkable 
case is that of the Ark-i-linik, a tributary of Hudson Bay, which is 
bordered for 200 miles (lat. 623^2° to 64^^°) by a nearly continuous 
belt of spruce, although the stream flows in the midst of the Barren 
Grounds.^ Undoubtedly in the last-named case the distribution is fa- 
vored also by the higher temperature of the seepage water on the lower 
slopes and valley floors during the autumn, a condition that prolongs 

» E. Wanning, CEcology of Plants, Ox. ed., 1909, pp. 28-29. 

2 For definition of physiological dryness see Schimper, Plant Geography upon a Physiologi- 
cal Basis, Ox. ed., 1903, p. 2. 

3 E. A. Preble, A Biological Investigation of the Athabaska-Mackenzie Region, No. Am. 
Fauna, U. S. Dept. Agri., No. 27, 1908, p. 48. Excellent for exact delineation of the continental 
tree line in northern Canada. 

41 



42 FOREST PHYSIOGRAPHY 

the growing season and mitigates the effects of extremely low air temper- 
atures. Some part of the effect may be attributed also to the deeper 
snows of the valleys which prevent extremely low ground temperatures. 

It is found that each species of plant requires its own specific water 
supply for most favorable conditions of growth, and that the quantity 
of water in the soil has a greater influence than any other condition on 
the distribution of plant species. To illustrate adaptations within a 
single genus the larches may be taken. Larix decidua prefers loose, 
well-drained soil and hence flourishes in dry situations where many 
other species die.^ It is partly to similar adaptations with respect to 
physiologic dryness that Larix sibirica owes its northerly range in Siberia 
where there is an extremely short growing season. The tamarack 
{Larix laricina) prefers a swamp habitat, though it will endure a hillside 
situation; it often occupies shallow lake basins recently reclaimed or 
partially reclaimed by lower forms of vegetation.- With the ascent or 
descent of the ground water new species may come in and old ones die 
out, so that changes in the level of the ground water have been found 
gravely to affect the character of the grasses and shrubs and even the 
trees of a region.^ 

The amount of water required by growing plants is large in propor- 
tion to the amount of dry vegetable substance produced. It varies 
according to the extent and structure of the leaf surface, the number 
and size of the stomata of the leaves, and~ the climatic conditions, 
especially the wind, which when strong and continuous has so intense a 
drying action on plants as sometimes to lead to special modifications of 
structure even when the ground is well supplied with moisture, a feature 
well developed in vegetation that occurs on windy mountain slopes. 
It has been found that the same plants use more water in humid than in 
dry climates, as if physiologic adjustment had been made in the latter 
case in response to a lessened water supply before the development of 
special structural adaptations. 

In general the amount of water required by a growing plant varies from 50 to 900 times 
the weight of the dry substance. Birch and linden transpire 600 to 700 pounds of water for 
every pound of dry matter fixed in the plant; oak, 200 to 300 pounds; spruce, fir, and pine, 
30 to 70 pounds; European evergreen oak, 500 pounds. What this means in terms of rainfall 
may be estimated from the last-named case, the European evergreen oak, which, with the water 
requirement indicated, and with 250 trees to the acre, and 40 pounds of dry matter per season 
to the tree, would require a rainfall of 22)^ inches per year. In general, about 15% of the 
rainfall is lost through plant transpiration. 

1 H. L. Keeler, Our Native Trees, 1905, p. 480. 

2 Idem. 

3 P. Feilberg, Om Enge og vedvarende Grasmarker. Tidsskr. Landokon. Kji^benhavn, 
p. 270. Quoted by Warming, p. 46. 



WATER SUPPLY OF SOILS 43 

Naturally the required amount of rainfall varies with the kind of soil, 
whether porous and nonretentive or compact and retentive, with the 
topography, and with the seasonal and yearly fluctuations in cloudiness, 
insolation, etc. The amount of rainfall necessary to the growth of 
forests is about the same as the amount necessary for agriculture with- 
out irrigation; that is, from 20 to 40 inches. Timber growth in regions 
having a mean annual rainfall less than the minimum amount is of so 
stunted a character as to be of little value. Furthermore the growth 
is so slow that once the timber has been removed by fire or lumbermen, 
the time necessary for a new growth is very great. ^ In studying the 
water supply of a region the lowest rainfall is of quite as much if not 
more value than the mean rainfall, for it is in a season of unusual drought 
that the growing trees may be most affected, so that in dry climates 
it is difficult to establish a forest without prohibitive expense.^ It is 
suggested that the cyclic changes in climate which appear to affect the 
entire earth might be studied to the benefit of the forester in planting 
forest seedlings, by enabling him to plant during the time of greatest 
rainfall so that an adequate root system shall have been developed before 
the advent of the driest years. 

The high water content of the soil may in part make up for the dry- 
ness of the air, as on the banks of streams in tropical savannas where 
lines of forest occur, or on steppes and deserts where trees are found near 
running water or where the ground water approaches the surface.^ This 
is, however, not a universal condition, for some plants flourish on very 
dry soil and in a humid air but are excluded from places with dry air. 
The heads of alluvial fans and cones where rivers leave mountain can- 
yons at the common border of mountains and piedmont plain are often 
covered with small patches of forest. The forest vegetation is main- 
tained by a kind of subirrigation or seepage through the porous sands 
and gravels of the fans. It often happens that this natural watering 
is too deep for agriculture and that forests in such cases grow where 
agriculture without irrigation is not possible.* 

As an instance of the effect of soil character upon the amount of soil 
water available for plants and hence upon the specific character of the 
vegetation may be mentioned the Steilacoom Plains, south of Tacoma, 

1 J. W. Powell, The Lands of the Arid Region of the United States, U. S. Geog. and Geol. 
Surv. of the Rocky Mountain Region, 1879, pp. 14-20. 

2 J. Wilson, The Modern Alchemist, Nat. Geog. Mag., vol. 18, 1907, p. 791; see also Rept. 
of the Sec'y of .^.gri. for 1907. 

3 J. W. Powell, The Lands of the Arid Region of the United States, U. S. Geog. and GeoL 
Surv. of the Rocky Mountain Region, 1879, pp. 15-16. 

■• Idem. 



44 



FOREST PHYSIOGRAPHY 



Wash., which have such an extremely porous soil of coarse gravel, with 
only a thin veneer of silt, that they constitute a locally semi-arid district 
in what is otherwise a humid region. The rainfall is about 44 inches 
per year, but percolation is so rapid in the loose stony ground that 
the district is a barren island surrounded by dense forests character- 
istic of the region. Instead of the Douglas spruce {Pseudotsuga taxifolia), 
the white fir (Abies grandis), the tideland spruce {Picea sitchensis), and 
the western hemlock {Tsuga mertensiana) , the district bears the yellow 
pine {Pinus ponder so) \ and species of gophers and the desert horned 
lark, which are at home in the dry districts east of the Cascades, are also 
at home in this restricted and peculiar area.^ 

The Coalinga district of California exhibits a plant distribution 
intimately related to water conditions. Certain gravelly and sandy 
beds of the district have superior absorptive capacity, while the adjacent 




Fig. 5. — Ideal section representing the ground water in relation to the surface and the bed rock. (Slich- 

ter, U. S. Geo]. Surv.) 

clay beds have but little power of absorption.'^ The sudden rains run 
off the clay beds without wetting them notably. The coarse beds are 
therefore marked by a varying abundance of vegetation; the clay beds 
do not support vegetation at all. The result is a marked parallelism 
and alternation of belts of vegetation and belts of barren country in 
sympathy with the belted outcrop of the strata. 

Forms of Occurrence 

Water is contained in the soil in three different ways — as ground 
water, as capillary water, and as hygroscopic water. 

GROUND WATER 

Ground water is the name applied to the water in the saturated zone 
of soil or rock ; it occurs from a few feet to a few hundred feet below the 
surface. Fig. 5; in humid regions it is found usually from five to fifty feet 

^ Willis and Smith, Tacoma Folio, Wash., U. S. Geol. Surv. No. 54, iSqq, p. 2. 
• Arnold and Anderson, Geology and Oil Resources of the Coalinga District, Cal., Bull. U. S. 
Geol. Surv. No. 398, 1910, p. 33. 



WATER SUPPLY OF SOILS 



45 



below the surface. The surface of the saturated zone or of the ground 
water is known as the water table or water plane. The depth of the water 
table below the surface varies in a striking way not only as between arid 
and humid regions, but also from place to place in a given region as 
shown in Fig. 6, because of topographic, soil, and other variations.^ 
The available pore space of the surface rocks occupied by water or 
moisture is generally about io% of their total volume. 

The water contained in porous soils and rocks as ground water is 
not stationary but possesses a very slow although perfectly definite 




Fig. 6. 



■Contour map of water table (continuous lines), showing direction of motion of ground water 
(arrows) and drainage lines (heavy lines). (Slichter, U. S. Geol. Surv.) 



motion as shown by geologic data which indicate very important chem- 
ical and physical effects due to permeating waters and by direct meas- 
urement of the rate of movement. The cause of the movement of 
ground water is gravity alone, and the rate depends upon the size 
of the pores, the total porosity, the pressure gradient in the direction of 
flow, and the temperature of the water, being more rapid the larger 
the size of the pores, the greater the porosity, and the higher the gra- 
dient and the temperature. The motion of the ground water as a 
whole is somewhat like the slow motion of a viscous substance, but is 
not generally in the nature of an underground stream as is ordinarily 
supposed. Underground streams may exist in limestone regions in 
great numbers, but they are on the whole exceptional hydrologic 

1 C. S. Slichter, The Motions of Underground Waters, Water-Supply Paper U. S. Geol. 
Surv. No. 67, 1902, p. S3- 



46 FOREST PHYSIOGRAPHY 

features. The general trend of moving ground water is into neighbor- 
ing streams and lakes; and the marshy zone on the borders of a valley 
flat, or on the bluffs of an intrenched vaUey, or on the shore of a lake, is 
a manifestation of the ground water appearing at the surface. In many 
dry western localities the ground water does not find its way immediately 
into the channel of the river, but takes a general course down the valley 
within the porous material of the valley floor; this movement, called 
the underflow, may often be utilized by constructing across the valley 
a subsurface dam which causes the ground water to rise to the surface 
or so near it as to become avaflable to plants. If a natural dam crosses 
the valley the effect may be a similar raising of the underflow and of the 
ground water, as is the case at the Bunker Hill dike near San Bernardino 
in southern California.^ A convergence of canyon walls will produce a 
similar augmentation of the water in a river because the underflow is 
forced to the surface. The debouchures of the rivers in such dry regions 
are usually marked by huge alluvial fans, as along the western base of the 
Sierra Nevada. In such cases both the underflow and the surface flow 
are distributed by a set of complex and anastomosing^ distributaries 
through gravelly fan deposits and so are gradually dissipated. Some- 
times the underflow may be quite independent of the water flowing in 
the surface channel. 

The surface of the water table is seldom level; the nearest approach 
to this condition is found in the case of a flat topography such as local 
areas of a coastal plain and of alluvial bottom lands. The surface of 
the water table shows a close sympathy with the surface contours of 
the land, although geologic conditions may greatly modify this general 
fact. Subsurface layers of impervious material may cause a rise and fall 
of the water table quite out of harmony with the surface contours, Fig. 5. 
The surface of the ground water is never fixed, for its level is responding 
continually to changes in rainfall, in barometric pressure, and in temper- 
ature by such important amounts as notably to affect the strength of 
flow of springs and flowing wells.^ 

After a rainy period has passed, the surface zone of saturation gradu- 
ally descends through the flowing off of water from the surface of the 
saturated zone, and continues to sink at a constantly decreasing rate 

1 W. C. Mendenhall, The Hydrology of San Bernardino Valley, Cal, Water-Supply 
Paper U. S. Geol. Surv. No. 142, 1905, p. 26, and plate 11, p. 72. 

2 A term applied to the characteristic branching and reuniting pattern exhibited by streams 
that terminate upon piedmont alluvial plains. 

3 A. C. Veatch, and others, The Underground Water Resources of Long Island, N. Y., 
Prof. Paper U. S. Geol. Surv. No. 44, 1906; also idem, Fluctuations of the water level in wells, 
with special reference to Long Island, N. Y., Water-Supply Paper U. S. Geol. Surv. No. 155, 
1906. 



WATER SUPPLY OF SOILS 47 

until another rainy season causes it to rise again toward the surface. 
The responses of the ground water to rainfall are not immediate, and 
depend upon the depth of the water table and the duration of both 
the rainy and the rainless period. It may happen that the water table 
is actually rising between rains and falling during a rainy period. The 
amount of such lag is usually rather small, however. In arid regions, 
where the ground water is far below the surface, say 100 feet, a rain 
of considerable magnitude may be absorbed by the dry surface layer 
and again reevaporated without replenishing the ground water at all. 
In humid regions light rains may be evaporated in the same way, but 
the water of prolonged rains is contributed to the ground water to the 
extent of 35% to 60%; the remainder is disposed of in the immediate 
run-off and by evaporation. 

Plants growing upon the soil rob it of moisture during the growing 
season to a degree that varies with the temperature, the kind of plant, 
and the texture of the soil, so that the amount of water in the soil dimin- 
ishes from spring to autumn, at which time the water table is at its lowest 
and may be from five to seven feet lower than in the spring. In the 
forest various species of plants act as weeds because they consume 
water before it reaches the roots of the trees. Shallow-rooted plants in 
the forest have on the whole a relatively small effect, however, because the 
greater supply of moisture for trees is derived from deeper lying sources. 

The level of the ground water is invariably lower in a forested tract, 
for the forest consumes water in exceptional quantities from the sub- 
soil; and this in spite of the fact that the surface soil of forested regions 
is as a rule moister than the surface soil of unforested regions. Many 
trees assume a peculiar shape or can not grow to normal height in a soil 
in which the ground water is near the surface.^ The forest sometimes 
has an important power in maintaining the soil water (not ground 
water) near the surface, i.e., not only the immediate surface but the 
whole surface zone in which the plant roots are found. The removal 
of the forest cover may in delicate cases destroy the capacity of the 
surface soil for water. Forest litter and particularly humus have high 
capacities not only for water but also for water vapor, and their de- 
struction by leaching, burning out through excessive oxidation, and 
the absence of any additions through fallen foliage, trees, twigs, etc., 
may cause a region that was once fairly moist to become dry. A con- 
crete instance is furnished by the Karst of Austria. This region lies 

1 For the rate of evaporation from a free water surface, from bare soil, and from soil covered 
with vegetation see R. Warington, Lectures on Some of the Physical Properties c^ the Soil, 
Oxford, 1900, pp. 107-126, where the results of Ebermayer, King, and others are discussed in 
detail. 



48 FOREST PHYSIOGRAPHY 

along the Austrian shores of the Adriatic and is composed of porous, 
fissured hmestone. For centuries it furnished the ship timber and wood 
suppHes of Venice, but excessive cutting, burning, and pasturing left it 
almost a desert waste, not only by decreasing the amount of soil water 
but also by allowing excessive soil erosion. Through government assist- 
ance 400,000 acres of the karst were placed under forest, beginning in 
1865, and the government has also backed up planting efforts by passing 
(1884) a reforestation law to control torrents.^ 

The beneficial effect of the forest in maintaining a soil cover by 
decreasing the delivery of ground water and retarding the immediate 
run-off is easily appreciated by recalling the fact that each of the water- 
ways in the forest is occupied by a perennial brook fed from the spongy 
soil, while the small stream beds of tilled land are dry except when rain 
is actually falling. The difference in the amount of erosive energy 
applied by the rain to the earth in these two contrasted conditions is 
very great. In the forest the rain creeps through the openings in the 
vegetal coating and moves so slowly that it does not expend any sensible 
energy upon the soil cover, while, if the surface is deprived of vegetation, 
the water may have a swift motion and an intense erosive force may be 
expended upon the incoherent soil.- 

The fact and rate of movement of the ground water may be determined 
(a) by the electrical method of Slichter,^ in which the gradual motion 
of the ground water from one point to another is determined by the use 
of an electrolyte which passes with the ground water in its general 
direction of movement; the method is very accurate, and is the standard 
one in use by the United States Geological Survey to-day; (b) by the 
use of the lysimeter, which is a receptacle inserted into the ground in such 
a manner that one side has an outlet discharging into a measuring 
gauge. It has been found by the Slichter method of measurement that 
the rate of movement is on the average from 2 to 10 feet per day for 
areas of moderate relief. A closer average figure is not possible because 
of the effects of variable soil texture, variable topographic and struc- 
tural gradients, differences in the amount and time of occurrence of 
rainfall, etc. 

Since the amount of soil moisture most favorable to plants (the opti- 
mum water content) is about half the maximum it can hold, it is clear 
that the saturated zone does not supply the most favorable conditions 

1 European Countries' Reclamation of Waste Land, Forestry Bull., Dec. 12, 1909, p. 2. 

- N. S. Shaler, The Origin and Nature of Soils, 12th Ann. Rept. U. S. Geol. Surv., pt. i, 
1890-91, p. 254. 

3 C. S. Slichter, The Motions of Underground Waters, Water-Supply Paper U. S. Geol. 
Surv. No. 67, 1902, pp. 48-51. 



WATER SUPPLY OF SOILS 49 

for plant growth. These conditions are supplied only in the zone 
immediately above the mean position of the ground water, where occa- 
sional immersion takes place through the raising of the water table but 
where opportunity is afforded for aeration and for the formation of 
plant foods without their being swept away immediately by movements 
of the soil water. Chemical decay and the formation of soluble plant 
foods take place in the soil only when a certain amount of water is 
present, but their most rapid rate is attained above the ground water 
not in it; with an excess of water the soil chemicals are too widely dif- 
fused upon their formation to effect soil changes of sufficient importance 
for the immediate needs of a plant. The most favorable conditions for 
the full utilization of the advantages of ground water are to be found 
in those places where the water table is from 5 to 10 feet beneath the 
surface, is relatively constant in position, the rainfall evenly distributed 
throughout the year, and where the vegetation is in the form of trees. 

It is noteworthy that the root systems of trees are very responsive to 
the ground water. A layer of feeding roots occurs in the surface soil 
where there is the greatest amount of soluble plant food immediately 
available, while the roots supplying moisture to the tree will be found to 
descend almost vertically to a point a little above the surface of the 
ground water, where a broad extension of the terminal roots may be 
found. Serious disturbance in the life of the tree is occasioned by 
sudden and unusually large changes in the level of the ground water, 
as through irrigation, which may raise the level of the ground water and 
cause the root terminals to suffer from want of aeration; or by too 
thorough underdrainage, either by tile or pumping, which may more or 
less permanently depress the water table and move it out of reach of the 
deep-lying roots adapted to a certain normal position. It is important, 
whatever the position of the ground water, that it be maintained at a 
relatively fixed position. Even short periods of immersion may work great 
injury to roots accustomed to perform their functions in an aerated soil. 

In an undrained soil the roots are confined to a shallow layer from 
which they quickly abstract the available moisture, and if the subsoil 
is clay the plant may suffer through the inability of capillarity to supply 
the needed amount of w^ter. In a drained soil the roots traverse the 
whole three feet or more into which air is admitted, and this mass of 
soil holds a very large quantity of capillary water. A water-logged soil 
is one in which the harm is not confined to the above results but extends 
to the solution of plant foods in superabundance and their removal in 
the water. The same condition also leads to the setting free of a large 
part of the nitrogen as nitrogen gas instead of its accumulation as a 



50 FOREST PHYSIOGRAPHY 

nitrate and to the breaking down of nitrates in the soil. Vegetable acids 
in exceptional amounts occur in wet soils, and in their presence bac- 
teria can not thrive. Earthworms and insects and the benefits derived 
from their action are excluded from all saturated soils. 

CAPILLARY WATER 

Capillary water is the most important form of water in the soil, since 
it is the normal means by which plants absorb food and sustain the 
rapid evaporation of the hot summer season. Furthermore, few plants 
have roots adapted to normal action in the saturated zone where free 
oxygen is not available. There is for all land plants a definite time 
limit beyond which their roots can not hve or at least remain healthy in 
a submerged state. The period is about three weeks for deciduous 
orchards when in their winter condition. 

In most cultivated soils the pore space is about 25% to 50% of their 
volume and this is known as their maximum water capacity or satura- 
tion point. The amount of this space occupied by water and required 
for the best development of plants is generally not more than 50% nor 
less than 40%, which means that the pore space must be about half 
filled with air for best results. All of these figures are subject to consid- 
erable variation in individual cases. For example, the maximum water 
content for lodgepole pine as it occurs in the dry hills about Sulphur 
Springs in Middle Park, Colorado, is 35% in loam and about half as 
much in sand and gravel. The optimum water content is between 
12% and 15%, rising to 20% where the rapid decay of the needle cover 
decreases the amount of available water. The minimum water content 
may fall below 5% in gravel without injury to the tree except in de- 
creasing its rate of growth.^ 

Loblolly pine also illustrates the great variation among trees in the 
amount of water they can endure. While this tree is adapted to a 
wide range of soils and can grow almost equally well on poor sandy up- 
land soils and low rich bottom lands, it everywhere requires an abun- 
dant supply of water. When the soil becomes dry the loblolly pine 
of Texas and North Carolina gives way ultimately to the longleaf and 
shortleaf pines. Its immediate occurrence in the zone of contest be- 
tween it and the other pines sometimes follows, not because the water 
supply is at an optimum for it but because its prolific seeding and rapid 
early growth cause it to come in more readily on land made vacant by 
fire or by lumbermen.- 

1 F. E. Clements, The Life History of Lodgepole Burn Forests, Bull. U. S. Forest Service 
No. 79, igio, p. 52. 

2 R. Zon, Loblolly Pine in Eastern Texas, Bull. U. S. Forest Service No. 64, 1905, p. 8. 



WATER SUPPLY OF SOILS 



51 



NATURE OF CAPILLARY ACTION 



The phenomena of capillarity depend upon the well-known fact of 
surface tension. If the molecular attraction of the particles of a solid 
for those of a liquid exceeds the attraction of the liquid molecules for 
each other, the Hquid adheres to or wets the soUd and the water rises 
until the pressure of the raised water column equals the pull (molecular 
attraction) of the solid upon the liquid.^ 

If a soil is saturated with water the whole pore space is filled, and, 
when this is allowed to drain away, some of the water is pulled down by 
gravity, but much remains 
clinging to the particles in 
a state of tension which 
just balances gravity. 
Reversing the process we 
find that water will always 
pass into the soil from a 
wet to a dry place until the 
film surrounding the par- 
ticles is evenly stretched 
throughout. The capil- 
lary rise of water in soil 
materials is well shown in 
the accompanying illustra- 
tion from Johnson, Fig. 7. 

The nature of capillary 
action is easily illustrated 
by the immersion in a 
basin of water of an open 

tube filled with soil. The water will rise in the soil of the tube to 
a height depending upon the temperature of soil and water, upon 
the amount of pore space in the soil, and upon the size of the capil- 
lary tubes or pores. The finer the particles of a soil the greater its 
water-holding capacity, the slower the capillary movement in a given 
unit of time, and the higher the ultimate capillary rise. The maxi- 
mum height of capillary rise thus far observed is 10.17 feet in 
material whose particles range from .0005 mm. to .016 mm. in diameter, 
although eighteen months are required to obtain the maximum. The 
rise of water in capillary tubes is at first rapid, but soon becomes 

1 For a complete statement of the laws of capillary action see any standard text-book of 
physics. 




Fig. 7. — Capillary water about soil grains, 
is the water table. 



The horizontal line 



52 



FOREST PHYSIOGRAPHY 



slower and after a few months usually reaches a maximum height be- 
yond which it can not rise. The most rapid continuous rise and the 
longest and ultimately the highest rise usually occurs in salty soils con- 
taining a small percentage of clay. Capillary movement takes place 
in moist soils much more rapidly than in dry soils, but the final adjust- 
ment as to height and water content will be the same. Wetting the 
surface layer or cooling it as in a cold rain tends to raise additional 
supplies from below, but in the latter case the action is probably to be 
attributed in part to the condensation of the evaporated subsoil moisture 
on coming into contact with the cool surface zone. 

Water will rise in the capillary tubes of the soil to a greater distance 
than will any other soil liquid. It is thought to be the limit of capillarity 
in trees which determines to a large extent the limit of their height. 



REGULATING ACTION OF THE SUBSOIL 

The subsoil acts as a regulator of the amount of water contained in 
the surface soil. It absorbs the water which percolates through the 
surface during the rainy seasons and yields water to the soil during the 
dry periods by capillary action. This is w^ell illustrated in the following 
table where the gain and loss of the surface layer are shown. 

RELATION OF THE SUBSOIL TO THE WATER CONTENT OF THE 
SURFACE SOIL 





Months and Days 


Water in inches 


30/iv 
to 

30/v 


30 /v 

to 
9/vii 


9/vii 
to 

7/ix 


7/ix 

to 

27/x 


Rainfall 


0.18 
3-45 

— I.O 

-2.27 


4-53 
2.96 
+ 1-4 

+0.17 


3-47 

5-71 

—0. 24 

— 2.0 


5.65 

1.83 

+0 61 


Evaporation 


Gain or loss of water in top foot . . . 


Water furnished by (— ), or passed on to (+) 
subsoil 


+3.21 





Since the changes in the water content of the surface layer are not 
represented by the difference between the rainfall and the evaporation, 
some water must in the one case have passed to the subsoil and in the 
other case have been lifted from it by capillary action.^ 

The studies of the Dnieper above Kiev during a twenty-nine-year period (1876-1905) 
appear to show that there is in certain periods an overconsumption by evaporation of the 
moisture stored in the soil and made available by capillarity. This overconsumption has to 
be supplied during the first wet year which follows one or more dry years, so that the amount 

1 A. D. Hall, The Soil, 1907, p. 95. 



WATER SUPPLY OF SOILS 53 

of evaporation may not in a given year be strictly the difference between the rainfall and the 
discharge, being less than this difference in wet years and greater in dry years. The influence 
of forests and marshes on the discharge in the summer of a dry year is to diminish the discharge; 
but in wet years the forest stores water.' 

The steady movement of capillary water toward the surface and its 
evaporation in the surface layer of soil results in highly beneficial effects. 
The upward-moving water holds in solution the soluble products of soil 
or rock decay, or both, and as it approaches the surface and is steadily 
evaporated it becomes more and more concentrated and may finally 
deposit its contained salts upon and among the soil grains. In either 
case enrichment of the surface soil or of the soil solution is the result. 
To be sure, the downward percolation of water, as after rains, neutralizes 
these effects to some degree, but since percolation is most active, almost 
wholly active, in the larger openings among the soil grains, and since 
downward percolation in the surface soil is an exceedingly temporary 
phenomenon, the contributions of plant food from below upward are more 
abundant than the losses by downward percolation. ^ A slow concen- 
tration of plant food thus goes on in the surface soil, and it is therefore 
in the surface soil that the feeding roots of plants are chiefly disposed. 
It is from the surface layer or layers that they derive their chief nu- 
trient substances; deeper- lying roots are mainly for supplies of water. 
In arid regions, where the ground water is far below the surface and 
the zone of weathering correspondingly deeper, and plant food more 
widely disseminated, plant roots are of course not confined to the sur- 
face soil. 

LIMITS OF ADEQUACY 

The entire amount of capillary water in the soil is not available to 
plants, for their roots are not in contact with all soil particles of the 
mass of earth they permeate, and, long before the mass as a whole has 
become dry, the particles in contact with the roots may be robbed of 
their moisture to such an extent that the soil may be said to be physi- 
ologically dry. In the case of certain apple trees in the arid region of 
California, 8.3% of water was sufficient to keep the trees in excellent 
condition on a loam soil, while on a clay soil 12.3% was too small an 
amount for proper growth.^ It is thus seen that the welfare of the 
plant is determined not by the total moisture content but by the free 
moisture held as capillary water by the capillary tubes. 

' E. V. Oppokov, nth International Navigation Congress, St. Petersburg, Russia, 1905. 
2 Cameron and Bell, The Mineral Constituents of the Soil Solution, Bull. U. S. Bur. Soils 
No. 30, 190S, p. 68. 

' R. H. Loughridge, Rept. Cal. Exp. Sta., 1897-98, pp. 65-96. 



54 FOREST PHYSIOGRAPHY 

HYGROSCOPIC WATER 

Dry soil if exposed to moist air absorbs water vapor, the rate and 
amount of absorption varying greatly with the character of the soil and 
the degree of saturation of the air to which the soil is exposed. The 
finer the particles the greater the capacity of the soil to absorb water 
vapor. Humus and finely divided ferric hydrates are substances with 
exceptional capacities for such absorption. Sachs has shown by experi- 
ment that the amount of moisture absorbed by dry soil as aqueous 
vapor may be so high in the presence of saturated atmosphere as to 
supply distinct portions of the normal vegetal demands. For example, 
in the arid regions the chief supply of water is derived through the 
deeply penetrating main roots; on the other hand the feeding roots of 
the plant, which are nearer the surface, are surrounded by soil that is 
almost air dry and yet slow growth and nutrition are possible. In 
such cases the water made available through the absorption of aqueous 
vapor is thought to be sufficient to have an effect upon vegetation 
especially in coast regions of summer fog, e.g., the coasts of California, 
northern Chile, and Peru. In the last-named cases a fog bank hangs 
over the edge of the land almost every night and frequently during the 
day at an altitude of 1 500 to 2000 feet, and a band of vegetation thrives 
at this elevation, whereas at lower and higher elevations the natural 
vegetation is much inferior or wholly lacking. 

High moisture absorption at night and its~ evaporation by day are 
also thought to prevent the rapid and undue heating of the soil and 
thus to improve the condition of plants under extreme temperature 
conditions. In humid regions where plants have become adapted to a 
higher water content hygroscopic water can not maintain plant growth, 
for wilting begins some time before even the capillary water is exhausted. 
Sachs ^ found that a young plant began to wither when the dark humus 
soil in which it grew still contained water equivalent to 12.3% of its 
dry weight; and plants were found to wither on loam and sand when 
the percentages of water fell to 8% and 1.5% respectively. A conser- 
vative estimate of the value of hygroscopic water would be that ordi- 
narily it has little if any value to plants directly; but, by increasing the 
amount of water in the soil that will be evaporated the following day, it 
lowers the temperature and thus indirectly increases the amount of avail- 
able water by decreasing the rate of evaporation.- 

1 J. von Sachs, Handbuch der Experimental-Physiologie der Pflanzen, 1865, p. 173. 

2 For velocity of flow of aqueous vapor through soil and its control by the dimensions of 
the apertures between the soil grains see Brown and Escombe, Static Diffusion of Gases and 
Liquids in Relation to the Assimilation of Carbon and Translocation in Plants, Phil. Trans., 
vol. 193, 1900, pp. 283-291. Abstract in Annals of Botany, London, vol. 14, 1900, pp. 537-542. 



CHAPTER IV 

SOIL TEMPERATURE 

EcoLOGic Relations 

There are for each plant certain air and soil temperatures most favor- 
able to development, known as optimum temperatures. The red birch 
(Betula nigra), peculiar among the birches in preferring a warm habitat, 
will grow in situations where important temperature changes occur, but 
it reaches its greatest size in the damp misty lowlands of Texas and 
the bayous and swamps of Florida and Louisiana. For most plants it 
is true that if the temperature at any time varies widely from the mean 
the activity of the vegetative functions is diminished or stopped, or 
the plant enters into a pathologic condition or dies. Beech, oak, and 
ash can survive in an air temperature of — 9.4° F.; their finer roots 
succumb to cold at from 8.6° to 3.2° F.^ 

Were the harm confined to mere stoppage of growth it would not 
be great, for a return to favorable temperatures would mean a revival 
of plant growth. But when during the summer season either seeds or 
plants remain in the soil at a temperature but little above the freezing 
point, bacteria and fungi of many varieties which are able to live at low 
temperatures may attack and destroy the vegetation. The limit below 
which most cultivated plants are practically inactive lies between 
40° and 45° F. Tropical plants usually germinate at a temperature of 
about 95° F. Even when seed germination progresses at a low temper- 
ature the rate is very greatly hastened by a higher temperature, and the 
same holds true of the normal growth of the plant. The temperature 
most favorable to germination and growth, and the degree of tolerance 
of high or low temperatures vary greatly with different plants; appar- 
ently each plant has become adapted to a certain mean temperature 
as well as to a certain range of temperature. Seeds and seedling plants 
should be put into the ground at a time when the temperature is most 
favorable for active growth, otherwise they may be destroyed by the 
micro-organisms of the soil. 

> C. von Mohl, Uber das Erfrieren der Zweigspitzen mancher gewisser Phycochromaceon. 
Bot. Zeitg., voL 41, 1848. 

55 



56 FOREST PHYSIOGRAPHY 

The degree of adaptation to cold made by some plants is quite remarkable. In the Arctic 
the shallow-rooted flora develops rapidly under the influence of continuous sunshine in the course 
of five to eight weeks. The seeds are capable of germination at very low temperatures, so that 
a mass of flowers may be found growing only a few feet from a snow bank or a glacier. The 
extreme conditions of development are easily appreciated. The ground is soaked with water 
nearly ice cold, and at a depth of only a few inches, and at the most but a few feet, ground ice 
may occur in large masses. But insolation during the period of continuous sunshine is very 
great and on June 21st surface insolation at the pole is almost as great as at the equator.i The 
conditions under which Arctic plants live during their short cycle of growth in the Arctic summer 
have been described in a number of records of experiments and observations among which 
are those noted below .2 

Soil temperature is of further importance in plant growth because of 
the stimulation which relatively high temperatures give to the useful 
bacteria of the soil, — bacteria which increase the supply of available 
nitrogen. It has been found that bacteria cease to develop nitric acid 
from humus when the temperature drops below 41° F., their action is 
of trifling importance when the temperature is at 54° F., it becomes 
vigorous at 58° F., but at extremely high temperatures the activity is 
reduced to a degree as unimportant as when too low temperatures pre- 
vail.'^ The influence of high temperatures in promoting rapid chemical 
action in the soil is shown by the sharp contrast between the highly 
decomposed soils of wet tropical regions and the moderately decom- 
posed soils of polar regions. The contrast is of course heightened by 
the greater rainfall in the tropics. 

Influence of Water on Soil Temperature 

Water has a predominating influence upon the temperature conditions 
of soils in humid regions. This is because the capacity of water for 
heat is about four or five times as great as the heat capacity of the aver- 
age soil, weight for weight; so that while one unit of heat is required to 
raise one pound of water 1°, the same change of temperature is produced 
in a pound of dry sand by the expenditure of .19 unit, and a pound of pure 
clay requires about .224 unit. Indeed water has the greatest capacity for 
heat or the greatest specific heat among known substances. This means 
that when the sun shines upon moist sand or clay a large amount of 
heat is expended in evaporating the water in it, while a relatively small 
amount is expended in raising the temperature of the soil particles. A 
well-drained field is therefore warmer on the whole than a poorly 

1 J. Hann, Handbook of Climatology, 1903, p. 93; R. DeC. Ward, Climate, 1908, p. 15. 

- M. Smith, Gardening in Northern Alaska, Nat. Geog. Mag., vol. 14, 1903, pp. 355-357; 
Raising Crops in the Far North, Geog. Notes, Jour. Geog., vol. 3, 1904, p. 91; Agriculture and 
Grazing in Alaska, Geog. Notes, Jour. Geog., vol. 11, 1903, pp. 528-529. 

3 F. H. King, The Soil, 1905, p. 224. 



SOIL TEMPERATURE 



57 



drained field and a dry soil warmer than a wet soil.^ It also follows that 
a fine-grained soil like clay will have a lower temperature than a coarse- 
grained and easily drained soil like gravel or sand. Hence clay soils are 
"cold" and sand soils are "warm." Were the clay and the sand air dry, 
the clay soil would be the warmer because its volume weight is less than 
the volume weight of sand. Since, however, few soils in the humid 
region contain no water, it is clear that clay will always be relatively 
cold and sand relatively warm under comparable conditions of water 
content. The following table summarizes the temperature differences 
between clayey and sandy soils, the table representing observations on 
a well-drained clay loam and a well-drained sandy loam. 

TEMPERATURE CONTRASTS BETWEEN SANDY AND CLAYEY SOILS ^ 



First Foot 


Second Foot 


Third Foot 


Sandy loam 

Clay loam 


76.5°F. 
69-5° 


74.7 F. 
69-3° 


72. 1° F.° 
67.0° 


Difference. . . . 


7.0° 


5-4° 


5-1° 



Soil Temperature and Chemical Action 

One of the first functions of soil water is to take into solution from 
the soil mineral substances which dissolve under all conditions with 
extreme slowness. It is here that the influence of soil temperature is 
perhaps as marked as in the beginnings of seed germination and plant 
growth in the spring. With a rise in the temperature of the soil chemical 
action becomes more effective, the supply of plant food in the soil 
rapidly increases, and osmosis and the diffusion of the dissolved material 
away from the soil and through the roots and other tissues of the plant are 
hastened. When we recall the fact that the soil air can occur in favor- 
able quantities only in a well-drained soil and that both high temper- 
ature and an abundant supply of air are necessary to many chemical 
reactions in the soil, it is clear that the conditions favoring a high temper- 
ature favor the disintegration of the soil minerals and the formation of 
available plant food. 

1 The exception to this condition may be noted in the autumn when the warmer soils are 
those containing the more water on account of the slow radiation of heat by water. The con- 
dition may be compared to that of a lake in the temperate zones, which is colder in summer 
but warmer in autumn and winter than the adjacent land. 

2 F. H. King, The Soil, 1905, p. 228. 



58 FOREST PHYSIOGRAPHY 

Influence of Slope Exposure, Soil Color, Rainfall, and 
Vegetation 

A rough surface will be colder than a smooth surface, 'other things 
being equal, because a larger surface of soil grains is exposed when the 
ground is rough than when it is smooth, and while the slopes exposed 
directly to the sun receive more heat than the sheltered slopes they lose 
more than they gain, by radiation and by contact with the air. This 
is overcome in agriculture by leveling the land or "rolling" it. The 
slope of the whole surface with respect to the sun's rays also has an 
important influence on the temperature of the soil. This principle 
is illustrated by Fig. 8. It will be seen that the slopes ad and dh 
are equal in gradient and length. The difference in the .amounts of 




SOUTH 



Fig. 8. — The influence of surface slope upon the amount of heat received per 
unit area. 



insolation is shown by the difference between 1-3 and 3-5, i-a, 2-e, 
etc., representing the sun's rays. Upon a fiat surface, as acb, the 
amount of heat received in the two cases is the same, that is, 1-4 equals 
4-5. It also follows from the diagram that the greater the relief the 
sharper the contrasts between the slopes directed toward the sun and 
those directed away from the sun, i.e., 1-2 is much smaller than 2-5. 
Southern slopes in the northern hemisphere are dry and warm, north- 
ern slopes are cool and moist, and the two often bear markedly different 
types of vegetation. Near Findelen, Switzerland, one may observe 
patches of snow on northern mountain slopes at elevations lower than 
the barley and rye fields on the southern slopes at 6900 feet.^ This 
difference is most marked in high latitudes and high altitudes combined 

1 H. E. Gregory (Gregory, Keller, and Bishop), Physical and Commercial Geography igio, 
p. 105. 



SOIL TEMPERATURE 59 

with strong local relief. It would be shown in the diagram by causing 
la — a ray of sunshine — to approach and finally to fall below ad. 
It is shown even in tropical situations close to the equator, though its 
expression in such a case is likely to be exaggerated by contrasts in 
rainfall derived from the trade winds. North of the equator these blow 
from the northeast and water the north or shadier (for most of the year) 
slopes copiously and leave the southern slopes dry; south of the equator 
the southeast trades produce a similar effect upon the southern or 
shady slopes. 

The temperature of the soil will be affected also by its color. Sandy 
soils are light in color and to that extent are cool because they reflect a 
great deal of sunlight from their white or light yellow surfaces. Dark- 
colored soils like dark loams and humus, and dark-colored rocks such 
as basalt and other basic rocks are raised to a higher temperature under 
comparable conditions of water supply and insolation. Humboldt 
found that a black basalt sand on the island of Graciosa reached a tem- 
perature of 147° F. while white quartz sand in the same situation 
reached only 122° F. Dark soils cool more rapidly at night than light- 
colored soils, but do not become colder than the latter. Among all 
known substances charcoal absorbs and radiates the sun's heat rays 
most powerfully, so that its absorptive power is taken as 100. Garden- 
ers and vine growers in the colder parts of Europe sometimes take 
advantage of the great absorptive power of carbon by spreading char- 
coal over the surface of the soil when early maturity is desired. The 
peasants of Chamouni hasten the melting of the snow by sprinkling slate 
powder over it.^ A similar practice has been observed among the 
Ladakhis in the upper Indus valley, where the peasants dig up earth 
in the fall, store it in the stables and houses all winter, and in the 
spring hasten the late melting of the deep snow by scattering the stored 
earth over it.^ 

One of the most effective means of increasing the soil temperature is 
through warm percolating rains which displace the cold soil water below 
the root zone. Its effect may be understood by recalling that the 
specific heat of water is higher than that of any soil by four or five times 
and that if a pound of rain water at 60° F. carry ten heat units into the 
ground each heat unit raises the temperature of a pound of sand, not 
one degree as would be the case with water, but four or live degrees. 
Cold rains produce the opposite result, and one of the most important 
beneficial effects produced by proper drainage of a forest area is the 

1 E. W. Hilgard, Soils, 1907, p. 304. 

2 E. Huntington, The Pulse of Asia, 1907, pp. 50-51. 



6o FOREST PHYSIOGRAPHY 

removal of cold water from the soil during the spring. If the region 
is one which is subject to summer droughts, such rapid removal of 
even cold water may be harmful, for the cold rains of spring would have 
less effect on the vegetation in delaying the beginnings of seasonal growth 
than would the lack of moisture in the dry season. 

A covering of vegetation, either living or dead, diminishes the soil 
temperature below that of bare fields. During different parts of the 
day these differences may rise to 4° or 5° F. a few inches below the sur- 
face and to far greater values at the immediate surface. The monthly 
averages of two localities rarely exceed i3/2° F.' The differences are 
greatest in the summer season, and when the covering of vegetation is 
thick the effect is more marked than when it is thin, so that forests 
exert a cooling influence and on the whole tend to diminish direct 
evaporation from the soil. 

Temperature Variations with Depth 

The effect of either extremely high or extremely low temperatures is 
felt in a surprisingly shallow layer at the earth's surface. In temper- 
ate regions the daily temperature variations affect only the surface two 
or three feet of soil or rock and vary according to the nature and con- 
dition of the soil material. 

The monthly variations reach to greater depths and the annual variations affect a layer from. 
35 to 75 feet in thickness. Below the zone of change the same temperature is found year after 
year, and though there are many exceptions to the rule, yet it is in general true that the 
deeper the point of observation the higher the temperature.' In the Arctic regions the level 
of no variation in temperature is but little below the surface in spite of surface variations 
between — 40^ and - 60° on the one hand and 80° and go° on the other. This is due to the 
presence of ice a short distance below the surface, and ice is a very poor conductor of heat. 
In the tropics the annual temperature variation affects the surface layer to a depth less 
than 2 feet because of the very slight seasonal changes in temperature. 

The temperature of the soil during the cold season generally exceeds 
that of the air; and the absolute minimum temperature of the soil is 
always higher than the absolute minimum temperature of the air during 
the cold season. During the warm season the soil temperatures in 
general exceed the air temperatures. In summer sandy soils are warm- 
est, loam soils next in order, and clay coldest; in winter these condi- 
tions are reversed. It is to the fact that soil temperatures are higher 
than air temperatures in cold situations and in all situations in cold 
seasons that render inhospitable localities possible to plants. 

Dew is sometimes derived from the soil owing to differences of tem- 
perature between soil and air. This occurs when the soil is warmer than 

1 The mean temperature of the earth's soil is estimated by Tabert to be raised by conduction 
from the internal heat of the earth by the trifling amount of 0.225° F. 



SOIL TEMPERATURE 6 1 

the air above it during a summer night. When the soil temperature 
falls to the proper figure dew is deposited within the soil to a depth 
at which the critical temperature is found. The daily repetition of 
this process at different depths exerts a considerable influence upon the 
distribution of moisture in the soil. It is probable that the formation 
of dew within the soil materially assists capillarity in distributing the 
soil moisture more uniformly. 

Recently an investigation has been made of the rate of flow of heat through the soil under 
certain standard conditions of moisture content, specific volume, and effective specific heat.' 
The practical value of the work lies in indicating the nature of the soil control which should be 
exercised in order to secure a warm seed bed and good germination in the preparation of forest 
seedlings, the handling of cranberry marshes, etc. It has been found that heat will pass from 
a soil grain to soil water 150 times easier than from a soil grain to soil atmosphere, and this 
points to one reason why an air-dry soil shows such low heat conductivity .2 Increase in heat 
conductivity due to the wetting of a soil is caused by a better contact between the soil grains. 
Coarse-grained soil has a lower heat conductivity than a fine-grained soil. A crumb structure 
in the soil causes the formation of air spaces, and the air acts as insulation against the passage 
of heat. When the soil crumbs are destroyed heat is conducted more rapidly and there is a 
more rapid rise of temperature.' 

' H. E. Patten, Heat Transference in Soils, Bull. U. S. Bur. Soils No. 259, 1909, pp. 1-54. 

2 Idem, p. 49. 

3 Idem, p. SI. 



CHAPTER V 
CHEMICAL FEATURES OF SOILS 

Relative Value of Chemical Qualities 

A SOIL can be considered fertile only when it possesses certain neces- 
sary physical qualities. If the physical condition excludes water, air, 
and plant roots, its stores of chemical substances remain locked within 
it, as useless as if they did not exist. It is also true that a soil poor 
in plant food and yet richly endowed with favorable physical properties 
may support an abundant vegetal growth. It is for these reasons 
chiefly that many investigators consider physical properties as para- 
mount in soil fertility. The chief objection to any rigid claims for 
either side of the contention regarding the relative value of physical 
and chemical properties is founded on the fact that physical and chem- 
ical conditions are often evenly balanced, and when the balance is 
destroyed it is as often because of unfavorable chemical as of unfavor- 
able physical conditions. An ecologist would see in the distribution of 
vegetation in the Coalinga district, Cal. (p. 44), or in the Steilacoom 
Plains, Wash. (p. 43), strong physical control of both plant distribution 
and plant species. On the other hand the strong chemical contrasts 
afforded by the various types of igneous and metamorphic rocks in many 
parts of the Laurentian area of Canada have very close counterparts 
in the vegetative contrasts,^ for the glacial and postglacial soils of the 
Laurentian area are thin and the rock character has equal opportunity 
with the soil character for vegetative expression. The almost universal 
abundance of moisture in the eastern part of the United States permits 
many variations in plant distributions based on chemical differences in 
soil and rock; in the West the general scarcity of water causes it to be as 
a rule the dominant factor in distribution. Chemical differences in soil 
have probably resulted in some cases in the development of new species of 
plants. Viola calaniinaria, for example, is thought to have arisen from 
Viola lutea by the action of zinc in the soil.- In the Alps there appears 
to be a wide difference between parallel species occupying mountains of 
limeless slate on the one hand and mountains of limestone on the other.' 

1 M. L. Fernald, The Soil Preferences of Certain Alpine and Subalpine Plants, Rhodora, 
vol. 9, 1907, pp. 149-193. 

2 A. F. W. Schimper, Plant Geography upon a Physiological Basis, Ox. ed., 1903. 

3 A. Kerner von Marilaun, Die Abhangigkeit der Pflanzengestalt von Klima und Boden, 
1858. Quoted by Warming. 

62 



CHEMICAL FEATURES OF SOILS 



63 



Each plant distribution is essentially the result of three groups of varia- 
ble factors — physical factors, chemical factors, and biotic factors. All 
three groups of factors must be comprehended. Only exceptionally 
is a single factor a determining factor in plant growth or distribution. 
It is much more common to find these results controlled by combina- 
tions of factors, some physical, some chemical, some biologic. By 
physiologic adjustment and structural adaptation plants still further 
diversify their character, extend their distribution, and complicate the 
problem of tracing a given effect back to its fundamental causes. 

Soil Minerals 

All soils are based to a greater or less extent upon the existence and 
destruction of fragments of rock-making minerals. Practically all the 
common rock-forming minerals are to be found in any ordinary arable 
soil, but the relative amounts may vary widely from those in the rock 
from which the soil was formed and from each other. This conclusion 
is true even in such apparently homogeneous substances as brick clays. ^ 
Retgers found 23 different kinds of minerals in the dune sands of Hol- 
land.- Examinations by the U. S. Bureau of Soils show that some of the 
mineral species of the soil present clear and unaltered faces, although 
frequently, and especially with the feldspars, alteration products may be 
observed on the mineral fragments. 

The composition of the chief minerals in the solid crust of the earth 
is shown in the following table. ^ 





•1 


J3 



-a 

en 


c 


V 

g 

3 


a 

'b 

3 

< 


3 u 

°."S 








100 
64.2 
68.6 
43-1 

45 

to 

50 

39 

to 

49 

41 
63. S 




















17 








18.4 

19.6 

36.9 

26 

to 

36 

3 

to 

15 








Feldspar \ Albite.. 


II. 8 














20 










6 

to 
10 



to 
i-S 








I 
to 


i Hornblende i ■. . . 1 


10 

to 

27 
49.2 
31-7 


10 
to 

15 


3 

to 
20 

9.8 




4-7 


1 Augite I 










Talc 












4.8 



















The soil minerals are all soluble to a certain extent in water, although 
the rate of solution may be quite slow and the actual amount dissolved 

1 Cameron and Bell, Mineral Constituents of the Soil Solution, Bull. U. S. Bur. Soils No. 30, 
190S, p. 9. 

2 L. V. Pirsson, Rocks and Rock Minerals, 1908, p. 280. 

3 A. D. Hall, The Soil, 1907, p. 16. 



64 FOREST PHYSIOGRAPHY 

at any one time small. Many of the soil minerals are in a very finely 
divided or pulverulent condition and are therefore easily attacked by 
chemical agencies such as water, oxygen, and the various soil acids. 
Among the important chemical substances in the soil that may be 
classed as mineral are the zeolitic compounds (the hydrosiUcates of 
alkaline earths and alkalies) easily decomposable by acids and capable of 
exchanging a part or the whole of their basic ingredients with solutions 
of other bases that enter the soil. The zeolitic compounds readily yield 
up a part of their ingredients to acid solvents and tend to fix a part or all 
of the soluble compounds that may be set free in the soil. The yielding 
up of their ingredients to acids is of great importance in that it enables 
plants to draw upon the reserve stores of food within the soil, the active 
solvent surrounding plant roots being water impregnated more or less 
with carbonic acid and possibly other acids. 

Perhaps nowhere outside the arid regions are the mineral and rock 
particles of the soil in such a fresh condition as in glacial soils; and to 
the presence of large quantities of undecomposed material in such soils 
may be attributed their prolonged fertility, although their immediate 
fertility may be far below that of rocks in a stage of more complete 
decomposition. 

Elements or the Soil 

Of the nearly 80 elements that have been identified in the earth's 
crust but 18 occur in important amounts. These arranged roughly 
in order of abundance are as follows: 

AVERAGE COMPOSITION OF LITEOSPHERE^ 

Oxygen 47-07% 

Silicon 28.06 

Aluminum 7 . 90 

Iron 4.43 

Calcium 3 . 44 

Magnesium 2 . 40 

Sodium 2 . 43 

Potassium 2 . 45 

Hydrogen •. . .22 

Titanium .40 

Carbon .20 

Chlorine .07 

Phosphorus .11 

Sulphur .II 

Barium 09 

Manganese .07 

Strontium 03 

Fluorine 02 

All other elements . ^o 

100.00% 
> F. W. Clarke, The Data of Geochemistry, Bull. U. S. Geol. Surv. No. 330, 1908, p. 32. 



CHEMICAL FEATURES OF SOILS 65 

In the higher plants that have been investigated up to the present 
time the elements indispensable to normal development are invariably 
ten in number: oxygen, hydrogen, carbon, nitrogen, phosphorus, sul- 
phur, iron, potassium, calcium, magnesium. If a single one of those 
substances is in a chemical form unavailable to the plant the plant 
enters into a pathologic condition or refuses to grow. Besides these 
ten substances all plants absorb various other substances whose utihty 
is unknown.^ 

Relations of Soil Elements to Plants 

While plants can not thrive in a soil that is without the substances 
noted above, the amount of each substance is found to vary according to 
the amounts of the others present; when a large percentage of lime is 
present, smaller percentages of potash, nitrogen, and phosphorus are 
required. But a soil entirely lacking in any one of these ingredients is 
an infertile soil. If the material of plants is burned the mineral residue 
contains potassium, calcium, magnesium, and a little iron among bases, 
and phosphorus, chlorine, sulphur, and silicon among non-metallic 
elements. Nearly all plants contain very small quantities of sodium 
and manganese; and radium, zinc, and copper have been found in traces 
in some plants. 

Among these various elements carbon, hydrogen, and oxygen are 
drawn from the air or the water, while the other substances, equally 
indispensable to the plant, are derived chiefly by way of the roots from 
the soil. This fact makes it unnecessary to have a complete chemical 
analysis of the soil to understand certain aspects of its fertility, since 
the non-essential substances in the soil are simply the physical media 
in which plants grow; they therefore have no chemical importance. A 
chemical analysis of a soil is required to show the amount of nitrogen, 
phosphorus, potassium, and calcium in the soil besides other substances 
of less importance. The determination of the carbon compounds of 
the soil is of importance, and of the carbonates of calcium and magne- 
sium which in most soils are active in neutralizing the acids that are 
harmful to bacteria.^ 

The degree of fertility of the soil, that is, the degree to which all the 
essential foods are present in available form, markedly affects plants 
in many ways, as, for example, the root habit of trees.^ The more 

1 E. Warming, (Ecology of Plants, Ox. ed., 1909, p. 55. 

2 A. D. Hall, The Soil, 1907, pp. 128-129. 

3 J. von Sachs, Uber den Einfluss der chemischen und der physikalischen Beschaffenheit 
des Bodens auf die Transpiration. Landw. Ver.-Sta., vol. i, 1859, p. 179. 



66 FOREST PHYSIOGRAPHY 

concentrated the nutrient solution of the soil the shorter the roots; 
and the poorer the soil the longer and more feebly branched are the 
roots; roots branch very copiously and form dense clumps in rich soil. 
In case of changing fertility with changing strata the roots display very 
marked contrasts in the degree of ramification within the different 
strata. In all such cases an unfavorable water supply in the otherwise 
richer medium will prohibit an exceptional root development in it. 

The same species will absorb various substances from different soils in 
different proportions. Individuals of the same species contain much 
silica if they grow in granite soil and much lime if they grow in cal- 
careous soil. Certain plants have the power of making both quantita- 
tive and qualitative selections of soil substances, and even when a 
desired substance is distributed in the soil in very small quantities such 
plants can in time absorb it in surprisingly large amounts. It is this 
selective power of root action combined with the fact that the sub- 
stances indispensable to plants occur in nearly all soils in quantities so 
considerable that almost every plant may extract more than the mini- 
mum amount, that results in the distribution of a given kind of plant 
upon soils of very widely different character. Furthermore each plant 
community and each plant species has its own peculiar economy, its 
own peculiar root system and general demands, which make it possible 
sometimes for many species to live side by side on the same soil with- 
out competing for food.^ 

Characteristics and Functions of the Principal Soil Elements 

OXYGEN 

Oxygen is the most abundant of the elements, forming about one- 
half of all known terrestrial matter. It is a constituent of nearly all 
minerals in both soil and rock, and occurs in most rocks in amounts 
ranging between 45% and 50%. It is present in the soil as air, has an 
important effect as free oxygen in the oxidizing of various soil minerals 
and substances to form oxygen compounds, and plays a very prominent 
part in the many chemical changes which take place in both soil and 
vegetation. Without oxygen the nitrifying bacteria, which are of the 
utmost importance in maintaining the supply of soil nitrogen, can not 
live, earthworms are excluded, plants die, and some of the chemical 
changes important in maintaining the supply of plant food suffer a 
diminished rate of action. 

^E. Warming, Oicology of Plants, Ox. ed., iQog, pp. 56-58. 



CHEMICAL FEATURES OF SOILS 67 

SILICON 

Silicon occurs in both soil and rock in the form of silica (Si02) or 
quartz. It is one of the most indestructible of natural compounds 
and is the prevailing constituent in nearly all sands and soils because 
of its great resistance, so that soils from whatever source derived will 
differ from each other mainly in the relative proportions of the siliceous 
and clayey constituents.^ Silica requires even in its most soluble form 
ten thousand times its weight of water for solution. Its relative in- 
destructibility causes it to accumulate to such an extent in practically 
all soils that it is a matter of no concern. While it is not an essential 
plant food it is important to plants as a medium in which their roots are 
disposed and anchored. The amount of silica (Si02) in the parent 
rock determines to a large extent the rate of weathering, the rate de- 
creasing with increasing quantities of this substance. Soil is derived 
from quartz schist, for example, with extreme slowness because of the 
resistance of quartz to weathering, and since this rock is composed 
chiefly of quartz its soil supplies but little plant food. Such a soil 
would be almost absolutely barren but for the frequent occurrence in 
the parent rock of accessory minerals that on decomposition yield im- 
portant plant foods. Sandstone and sandy soils are usually poor be- 
cause the sand almost always consists chiefly of quartz grains and the 
finer portions alone are of importance in plant nutrition. The oxide 
of silicon is the principal constituent of quartz sand; with it are usually 
associated how^ever particles of other substances so that even a beach 
sand may have all the necessary elements for the limited growth of 
plants. 

ALUMINUM 

Next to oxygen and silicon the most important element is aluminum. 
It is the most abundant of all the metals and occurs chiefly in combina- 
tion with silicon and oxygen, forming an important series of minerals 
known as aluminous silicates, such as feldspars, micas, zeolites, etc. 
Aluminum is so easily oxidized that (with the exception of the fluorides) 
only oxidized compounds of aluminum occur in nature. As a silicate, 
aluminum occurs as the principal constituent of all clays, and while in- 
soluble in this form, soluble potash, lime, etc., are usually associated with 
it. Chemically pure clay is very insoluble and of little importance for 
it is the end product of the chemical decomposition of the soil minerals 
enumerated above, but it is very important in its capacity to retain 
soluble salts. The physical action of clay in producing flocculation and 
tilth has already been described (p. 37) and is of the highest importance.. 

' Smith and Macauley, The Mineral Resources of Alabama, Geol. Surv. Ala., 1904, p. 74. 



68 FOREST PHYSIOGRAPHY 



IRON 



Iron gives a characteristic reddish or yellowish color to soils, occurs 
on the surface of the earth as an oxide and at greater depths or on fresh 
rock surfaces as a carbonate, sulphide, or silicate. Its principal forms are 
hematite, limonite, magnetite, pyrite, etc. It is essential to plants in 
the development of chlorophyll, without which there is improper nutri- 
tion. On account of its almost universal distribution in some form or 
other it is not a matter of concern in soil fertility. 

CALCIUM 

Calcium occurs in combination with carbon dioxide in great abundance 
in limestone; in the form of calcium carbonate it is slightly soluble in 
water containing carbonic acid and hence is an almost universal ingredi- 
ent of all natural water. It is an important constituent of the principal 
silicates. It is one of the most essential substances in the soil because 
of its physical effects (p. 29) and because of its direct use in the formation 
of plant substances. 

We have already noted the effect of lime, the carbonate of calcium, in 
promoting tilth, though it should be observed that an excess of 2% lime 
does not increase the tilth of the soil. Besides this it favors the impor- 
tant process of nitrification by prohibiting that acidity which excludes 
the nitrifying bacteria (p. 8S). It seems to be an established fact that 
about 1% of lime is a high percentage of this ingredient in virgin soils. ^ 
In this connection it is important to see that when a large proportion of 
lime carbonate is present in the soil lower percentages of potash, phos- 
phoric acid, and nitrogen are adequate. Among the other influences of 
lime in the soil are the rapid conversion of vegetable matter into black 
neutral humus and an increase in the nitrogen supply, an acceleration of 
the oxidation of carbon and hydrogen, a counteracting of the injurious 
effects of an excess of magnesia and of soluble salts in alkali lands, and 
a liberating effect upon the potash held in zeolitic compounds. An 
excess of lime, from 8% or more, disturbs nutrition, suppresses or dimin- 
ishes the formation of chlorophyll and starch, and is in general dele- 
terious to plant growth. 2 

The longleaf and shortleaf pine regions of the United States are 
poor in lime and have long remained almost uncultivated; the excess 
of lime in many of the chalk lands of Europe causes them to be equally 
infertile. The maritime pine and chestnut tree are both antagonistic 
to lime and any considerable amount of it will cause them to die or to 

> E. W. Hilgard, Soils, igo7, p. 346. 

2 For a discussion of lime effects see E. W. Hilgard, Soils, 1907, pp. 378-381 et al. 



CHEMICAL FEATURES OF SOILS 69 

deteriorate, in contrast to the Corsican pine, which is a lime-loving 
tree. 

The higher the clay percentage of a soil the more lime carbonate it 
must contain in order to exhibit the advantages of a calcareous soil. 
In sandy lands a characteristic lime growth may reflect the presence of 
only 0.10% of lime, while in heavy clay soils 0.6% is required to produce 
the same result. This explains the prominent color of dark-tinted 
humus in sand soils when very small amounts such as 0.2% of lime 
occur, whereas a comparable effect is produced in clay soils only when 
the percentage rises to 1%. A soil that effervesces with acids contains 
at least 5% of carbonate of lime, and percentages so small as to make the 
soil distinctly calcareous are not distinguishable by this mode of analysis. 

In the study of the effect of lime upon vegetation a difference of opinion 
has arisen, probably due to the very different methods pursued and the 
different regions in which the students have worked. Hilgard, who has 
done the most extensive work of this character in America, concludes 
that the moisture of the soil is the point of first importance in the dis- 
tribution and welfare of vegetation but that the condition next in impor- 
tance is the amount of lime present. He grants, of course, that certain 
species are indifferent to lime, but holds that most species respond to 
lime in a marked manner and that on the whole the presence of lime 
tends to greater fertility except in the obvious case where it is present 
in excess. He finds that in Mississippi and Alabama there is a marked 
correspondence between the growth habit and types of trees and the 
geologic formations, so that a geologic map of the region would also be 
to a large extent a map of the various tree zones. The conclusions of 
Hilgard are of great value because they were formulated as early as 
i860 after extensive study of native vegetation which grew in a soil that 
was almost undisturbed by man, hence a vegetation that represented 
a long term of adjustment to the soil. This is obviously an advantage 
over the conditions in Europe, where the observers of the vegetation have 
quite constantly to eliminate the influence of cultivation and other 
disturbing influences due to the long occupation of the land by man. 
It would not be fair, however, to dispose of the matter by merely stating 
the ground of Hilgard's conclusions. The contentions of the European 
students are cogent and interesting and deserve equal attention here. 

Warming says: 

"Although the characteristics of the lime-flora are clear and distinct, yet in the past the 
influence of lime upon vegetation has been overestimated. Indeed, a distinction has been 
made between calciphilous and calciphobous plants. Recently it has been definitely established 
that the amount of lime in itself, in so far as it does not operate physically, can not be the cause 
of differences in the flora, for not only can calcicolous plants be cultivated in soil that is poor 



70 FOREST PHYSIOGRAPHY 

in lime, but silicicolous plants, and even bog-mosses, which are regarded as preeminently 
calciphobous, can grow vigorously in pure limewater if the aqueous solution be otherwise poor 
in dissolved salts. It has been overlooked that nearly all lime soils are rich in soluble mineral 
substances, and this wealth excludes plants belonging to poorer soils; beyond this the important 
physical characters of calcareous soil, compared with granite soil, come into play."i 

In general the disagreement of the conclusions as to the power of 
lime to control plant distribution appears to be due to the absence 
of a standard conception as to what constitutes a lime soil. By some 
a soil is regarded limey only when it effervesces with acids, yet not 
less than 4% of calcium carbonate in a soil will respond to the acid 
test, whereas 0.1% will have important effects 6n plants provided the 
soil is sandy. So far, most of the conclusions have been mere obiter 
dicta. The conclusions of American investigators, based on native 
and practically undisturbed vegetation, are essentially sound, though 
they require important modifications where the physical conditions 
become extreme. 

MAGNESIUM 

Magnesium forms an essential part of the rock known as dolomite 
and may exist as a silicate in such rocks as serpentine, talc, etc. In 
igneous rocks it occurs in the minerals pyroxene, mica, olivine, etc. 
Magnesia is invariably and rather abundantly found in the seeds of 
plants and is a very important plant-food ingredient, but must not 
occur in excess or it will cause, through chemical action, a pronounced 
change in the capacity for imbibition, and thus particularly disturb the 
functions of the plant. Magnesia is especially concerned in the transfer 
of phosphoric acid through the plant tissues; while magnesia predomi- 
nates in the fruit of a number of crop plants lime predominates in the 
leaves, so that there is apparently a connection between the extension 
of leaf surface and the lime requirement. 

SODIUM 

Sodium occurs in largest percentage in the igneous rocks as a con- 
stituent of the soda-lime feldspars, amounting on the average to 23^^% 
of the igneous rocks. These feldspars are more readily attacked by 
water and carbon dioxide than are the other common minerals save 
certain basic silicates, so that the whitening and the softening of felds- 
par is one of the first signs of rock decay. The sodium salts are so 
soluble, however, that they are leached away almost as rapidly as formed, 
with the result that soils are normally rich in potash but poor in soda. 
In poorly drained soils of arid lands, however, these qualities result in 

' E. Warming, CEcoIogy of Plants, Ox. ed., igog, p. 58. 



CHEMICAL FEATURES OF SOILS 7 1 

a concentration of soda through the continued evaporation of ground 
water, where as carbonate, sulphate, and chloride it gives rise to alkali 
tracts poisonous to all but specially adapted species of plants. In 
northern Chile, one of the most arid tracts of the world, the sodium 
has become concentrated in nitrate deposits. These on account of the 
fixed nitrogen which they contain are extensively mined and shipped to 
many agricultural regions in humid lands as a fertilizer. Thus through 
its chemical properties — the extreme basicity of the element and the 
solubility of its salts — sodium causes the most arid deserts to add to 
the fertility of the garden spots of the world. Sedimentary rocks, the 
accumulations of the constituents of soils of former ages, are usually 
deficient in sodium and may be almost free from that element. Their 
soils, the result of a second cycle of leaching, tend to be still more 
barren in sodium. The use by land plants of potassium is doubtless 
an adjustment to the prevailing composition of soils; marine plants, 
living in an environment where sodium is dominant, show a parallel use of 
sodium in their tissues though they use potassium also, to some extent. 

POTASSIUM 

One of the most important elements of the earth's surface from the 
standpoint of plant growth is potassium, which in the form of a nitrate 
is found in nature (saltpeter). It occurs in small and large quantities 
in a great variety of igneous and metamorphic rocks, but may be 
absent from sedimentary rocks. It is present in mica, amphibole, 
and pyroxene, and when combined with silica is an important member 
of orthoclase and other minerals. Granite soils generally contain a 
good supply of potash on account of the common occurrence of potash 
feldspar in them. Granite soils may be deficient in lime, however, 
unless hornblende is present, since lime-feldspar is not likely to occur 
as an accessory ingredient of granite. 

The amount of potash necessary for high soil productivity is about 
0.5% and at this figure the addition of potash has but little effect upon 
the fertility. At 0.25% there is a deficiency that must be made up by 
fertilization. These figures do not apply, however, in arid or tropic lands. 
In tropic lands the prevailingly high temperature, the great rainfall, and 
the continuous leaching, cause a very rapid liberation of potash from its 
insoluble form as well as its rapid removal; smaller amounts are there- 
fore necessary at any given moment. In arid regions the absence of rapid 
leaching allows the accumulation of earthy salts of many kinds, among 
which potash is prominent.^ 

' E. W. Hilgard, Soils, 1907, pp. 3S4-3SS- 



72 FOREST PHYSIOGRAPHY 

PHOSPHORUS 

Of very high importance in soil fertility is phosphorus, found in the 
minerals vivianite and apatite, in the bones of animals, and m the seeds 
of plants. Apatite (phosphate of lime) is an almost universal constituent 
of granitic rocks, but occurs in very small quantities.^ The amount of 
phosphoric acid (P2O5) contained in granitic rocks rarely exceeds 0.2% 
and may fall as low as 0.05%; but small as the amount is it probably 
is the main source of supply of phosphates existing in the soil. Phos- 
phorus is most abundant in the basic eruptive rocks such as diorites 
and gabbros and deficient in such rocks as sandstone and slate. 

Where the minerals vivianite and apatite are abundant in the country 
rock, as in the basaltic lavas of Hawaii, phosphoric acid may be pres- 
ent in the soil in exceptional amounts, — nearly 2%. Unfortunately 
in this particular case it occurs in the form of an insoluble basic iron 
compound, ferric phosphate, which is dissolved with such difficulty that 
it is wholly unavailable to vegetation and the soil containing it is actually 
phosphate poor. The same is probably true of certain ferruginous soils 
in California and the South. The lower limit of adequacy of phosphoric 
acid in the soil is about .05%. Exceptionally soils may contain as much 
as .30%, while .15% is regarded as adequate. In non-ferruginous lands 
the amount required is smaller than in the case of ferruginous lands 
because the iron renders phosphoric acid inert by forming ferric phos- 
phate, an insoluble substance." 

Phosphate deposits are derived chiefly from animal remains, but 
animals derive it from plants, which in turn depend for their supply 
upon the alteration products of apatite. Commercially important 
deposits of apatite occur in Spain, Canada, and Norway. From the 
Norwegian deposits a commercial fertilizer is now manufactured, a 
phosphoric-chalk manure. Phosphorus is one of the rarest essential 
plant foods, and its conservation should be a matter of great concern. 
Sewage contains relatively high percentages of it, and the application of 
sewage to the land instead of its wastage in rivers and the sea is one of 
the most important though as yet limited uses of this neglected fertilizer. 

SULPHUR 

Sulphur plays an important part in the nourishment of plants, since it 
is an essential constituent of vegetable albumen and allied compounds, 

1 The pure crystalline mineral apatite rarely occurs in large masses. Minute crystals of it 
are found widely scattered in many rocks, granite, basalts, etc. The largest deposits occur in 
connection with carbonate of lime in rocks known as phosphorites which closely resemble 
limestone. Extensive phosphate deposits are found in southern Cahfornia, Florida, Alabama, 
Tennessee, Kentucky, Wyoming, Utah, Idaho, Montana, etc. 

2 E. W. Hilgard, Soils, 1907, pp. S93 et al. 



CHEMICAL FEATURES OF SOILS 73 

hence a soil to be fertile should always contain sulphates in available 
form. The usual form of occurrence is in combination with the metals 
to form sulphides or with oxygen and a metal to form sulphates. It is 
an essential part of the mineral pyrite, and when combined with oxygen 
and calcium forms the valuable fertilizer gypsum. The amount of 
available sulphur existing in any soil is usually very small. The relative 
available amount in ordinary soils is indicated in the following table, 
in which it is assumed (i) that the mean dry weight of a surface foot 
of soil is 80 pounds, and (2) that the amount of soluble material is 
accurately represented by the results of a large number of analyses 
collected in the Tenth Census Reports. 

RELATIVE AMOUNTS OF CERTAIN ESSENTIAL PLANT FOODS IN AN ACRE-FOOT i 

Potash in surface foot, per acre 3-76 tons 

Soda in surface foot, per acre 1.58 " 

Magnesia in surface foot, per acre 3.92 " 

Lime in surface foot, per acre i . 88 " 

Phosphoric acid in surface foot, per acre i . 97 " 

Sulphuric acid in surface foot, per acre 91 " 

Soluble silica in surface foot, per acre 73 ■ 40 " 

In the decomposition of the various compounds of iron and sulphur, oxi- 
dation affects either or both the iron and the sulphur; when the iron alone 
is oxidized the sulphur or some part of it separates as hydrosulphuric, 
sulphurous, or sulphuric acid. The sulphur of the hydrosulphuric 
acid may be later oxidized to sulphurous or sulphuric acid through the 
action of water and oxygen with or without the assistance of bacteria, 
though bacteria are often the inciting cause of the oxidation. In the 
form of sulphuric acid sulphur is immediately available to plants, indeed 
sulphuric acid itself is found in the tissues of plants in small quantities. 
It is subject to steady depletion in this form by percolating water and 
by combination with bases in the formation of sulphates, in addition to 
the demands upon it by growing vegetation. ^ 

Total Plant Food; Available Plant Food 

The data concerning plant food are to be distinguished from those 
derived by mere chemical analyses of soils, which in themselves are of 
small value in understanding ecologic conditions. Almost all soils 
show on ultimate chemical analysis an abundance of the elements re- 
quired for almost any given crop, but there is the widest difference 
between the forms in which the elements occur, so that it is the available 
plant food, and not the ultimate amount of plant food that may be 
produced on complete decomposition, that is a matter of chief interest 

1 F. H. King, The Soil, 1905, p. 102. 

2 C. R. Van Hise, A Treatise on Metamorphism, Mon. U. S. Geol. Surv., vol. 47, 1904, p. 468. 



74 FOREST PHYSIOGRAPHY 

in the study of the chemistry of soils. The soil must be regarded as 
possessing most of its plant food in such a state of combination that it 
can not be utilized by the plant directly, but must by weathering slowly 
pass into the soluble, i.e., the available, form. 

Determination of Soil Fertility 

The approximate chemical nature of an ordinary soil may be ascer- 
tained in a direct manner by the determination of both the decomposed 
and undecomposed minerals present in it. The determination of its 
fundamental nature requires an examination of the undecomposed 
minerals only, since it is presumed that the decomposed part of the soil 
has been derived from the constituent minerals and since the undecom- 
posed material forms by far the greater bulk of the soil. But such 
an analysis is of less value than direct qualitative and quantitative 
chemical analyses of the soil character. Even the latter analysis does 
not always furnish a reliable guide as to the productivity of the soil. 
The previous history of the land and the physical characters of the soil 
may be predominating factors. 

In attempting to ascertain the nature and amount of the decomposed 
portion of the soil various working plans, which attempt to imitate plant 
action, have been tried. The water-soluble ingredients of the soil are 
only a portion of the total number of substances upon which plants may 
draw for food, because the plant roots act not alone through the me- 
dium of water but also through water charged with carbonic and possibly 
other acids. Clearly, then, the action of plant roots may be imitated 
more closely by employing in the analysis a weak acid solvent that will 
act upon the soil in a manner similar to the soil acids. The weak acid 
solvent employed is empirically determined, for no one has yet analyzed 
the soil about a growing plant in such a way as to ascertain under pre- 
cisely what conditions the various soil acids act. The results of soil 
analyses by means of weak acid solvents must be compared with cultural 
experience and observations on natural plant growth; the results are thus 
empirical approximations, but they are the best that have been achieved. 
It has been found by such observations that all soils are continuously 
soluble to some extent but that the differences between the solutions 
derived from soils of low and of high productivity are very striking. 

Plants differ very greatly in the energy and quality of their action 
upon reserve soil ingredients, so that no single solvent used in an analysis 
could properly represent the action of plant roots in general. Among 
the many solvents employed for the purposes of soil extraction and the 
determination of immediate soil productivity are citric acid (a i% solu- 



CHEMICAL FEATURES OF SOILS 75 

tion is most commonly employed) and aspartic acid, among the weak 
acids; and hydrochloric, nitric, and a few others, among strong acids. 
The hydrochloric acid is employed in densities ranging from i.i to 1.16, 
while a density of 1.115 has been found most convenient and satisfactory 
of all. From experience with acids of different strength it has been 
found that a five-day period of digestion with hydrochloric acid (density, 
1. 1 1 5) is sufficiently effective in showing what plant-food ingredients 
of the soil maintain its permanent productive capacity. This appears 
to be the natural limit of the action of the acid upon the soil and pro- 
duces a maximum effect. There is much to justify the contention that 
the only legitimate solvent in determinations of soil fertility is carbonic 
acid, the commonest, the natural, and the most abundant acid in the 
soil.^ The immediate soil requirements may also be empirically deter- 
mined with a fair degree of accuracy by analyzing the ash of the vege- 
table growth and establishing a ratio between the normal ash ingredient 
and the actual soil ingredients. It has been found that in the case of a 
deficiency of certain kinds of plant food there is a disturbance of nutri- 
tion that manifests itself in the form or in the development of the plant 
and affords a direct basis for future determinations of a similar sort 
without the repetition of the full chemical analysis of the ash. 

Unless extreme physical characters interfere with normal plant growth 
virgin soils showing high percentages of plant food as determined by 
extraction with acids- (hydrochloric, nitric, etc.) invariably prove highly 
productive. Hilgard states the law as follows: "The actual amounts of 
soil ingredients . . . rendered accessible to plants are . . . more or less 
proportional to the totals of acid-soluble plant-food ingredients present." ^ 
The natural condition which this result indicates may be stated thus: 
the larger the total amount of plant food in the soil and ultimately 
available the greater will be the immediate effect of the weathering agen- 
cies that produce available plant food. This conclusion appears to be 
rather well established and indicates how high a degree of importance 
should be attached to the chemical composition of soils despite the 
relatively higher importance of physical qualities in general. Neither 
group of qualities can be adequately applied to a soil type to the ex- 
clusion of the other group. All the field conditions must be evaluated 
before a soil analysis can be regarded as complete. It is in the highest 
degree unscientific longer to advocate the supreme importance under all 
circumstances of a single group of soil qualities. 

1 A. D. Hall, The Fertility of the Soil, Science, n. s., vol. 32, 1910, p. 366. 

2 E. W. Hilgard, Soils, 1907, pp. 343-353. etc. 

3 Idem, p. 346. 



76 FOREST PHYSIOGRAPHY 

Harmful Organic Constituents of the Soil 

In concluding this discussion of some of the chemical properties of 
soils it seems desirable to note an important recent result in one 
of the most complicated branches of soil chemistry, the " identification 
of harmful organic substances that occur in the soil, the determina- 
tion of their properties and the formulation of remedies to offset their 
effects. It has been found that many plants can possibly excrete, as 
the result of growth, organic compounds which are poisonous to the 
plants producing them. It has been found that these organic substances 
while inhibitory to the plants which produce the^tn have little or no effect 
upon other plants. It is therefore concluded that they may be positive 
forces in producing a natural succession or rotation of wild vegetation 
not explained by any change of soil or climate.^ 

These harmful substances are constantly being added to the soil, and 
some of them are injurious in quite small amounts and are a cause of 
infertility even when the amount of plant food in the soil is abundant.^ 

The most markedly harmful bodies are found within the plant but are not apparently 
an essential part of the life of the plant. Of this class are arbutin, vanillin, heliotropine, ter- 
penes, etc., all of which are very injurious. Tyrosine is injurious in quite small amounts, 
while some of the protein decomposition products are not only harmless but appear to act as 
plant nutrients; such for instance are asparagine and leucine.^ The harmful substances have a 
toxic effect on the plants, but are destroyed or rendered harmless by other substances like soda 
and lime in cooperation with plant roots. O.xidation in a high degree converts some of these 
bodies into harmless substances, but a low rate of oxidation causes the organic matter to 
decompose incompletely and gives rise to organic compounds unfavorable to plant growth.* 

Hall suggests that these so-called toxic substances may be normal 
products of bacterial action upon organic residues in the soil and that 
as such they may be as abundant in fertile soils rich in organic matter 
as in the sterile soils from which they were extracted. He points to 
the great power of the soil in precipitating soluble materials within it 
as a possible natural remedy for such toxic substances.^ 

It has also been found that tree roots have a toxic effect on the growth of wheat. The 
absence of grasses about certain trees is thus attributed not to depletion of plant food alone 
but to the toxic effects of the tree roots heightened by shade and the well-known injurious 
effects of washings from trunk and leaves." 

1 Schreiner and Shorey, The Isolation of Harmful Organic Substances from Soils, Bull. U. S. 
Bur. Soils No. 53, 1909, pp. 1-3. 

2 Idem, p. 29. 

3 Idem, pp. 12-13. 

■• Schreiner and Reed, Certain Organic Constituents of Soils in Relation to Soil Fertility, 
Bull. U. S. Bur. Soils No. 47, 1907, p. 13. 

5 A. D. Hall, the Fertility of the Soil, Science, n. s., vol. 32, 1910, p. 367. 

« C. A. Jensen, Some Mutual Effects of Tree Roots and Grasses on Soils, Science, n. s., 
vol. 25, 1907, pp. 871-874. 



CHAPTER VI 

HUMUS AND THE NITROGEN SUPPLY OF SOILS 
Sources and Plant Relations 

The nitrogen of the soil is a matter of paramount importance in fores- 
try, especially in the maintenance of a proper forest growth and in efforts 
at reforestation, for as we have seen a supply of nitrogen in some form or 
other is absolutely indispensable to plants.^ We shall therefore discuss 
it somewhat more fully than the other plant foods of the soil. To be 
available to plants nitrogen must be in soluble form, and it is therefore 
as a nitrate that it is used by the plant. The main source of nitrogen is 
humus, whence it is derived chiefly by bacterial action; although nitrogen 
exists in unhumified organic matter it is not in an available form. Other 
sources of nitrogen are {a) nitrogen-fixing bacteria that live in a free 
state in the soil and derive their nitrogen from the soil air, (b) nitrogen- 
fixing bacteria that live in symbiotic association with legumes and other 
plants, and (c) rain water. The amount of nitrogen contributed to the 
land in the last-named manner amounts to a half pound or a pound or 
more per acre with a rainfall of about 30 inches per annum.^ 



NITROGEN BROUGHT TO THE SURFACE OF THE EARTH BY RAIN 
(Pounds per acre per annum.) 





Nitrogen 




Locality 


Ammoni- 
acal 


Nitric 


Total 


Remarks 


Rothamsted, England 

Barbados 


2.823 

1.009 

I-3SI 

2.63 

5.06 


0.917 
2.443 
2. 190 
1.06 
.356 


3-74 

3-452 

3-541 

3-69 

S-42 


In 1888-89 
S years' average 
7 years' average 
3 years' average 
Do. 


British Guiana 


Kansas 

Utah... 



Nitrogen is usually the first element to become exhausted in the soil 
because the nitrates are exceedingly soluble and no part of the soil has 
any special power of holding back nitric acid when it passes in aqueous 
solution through its pores, so that the nitric acid produced in the soil 

» A. D. Hall, The Fertility of the Soil, Science, n. s., vol. 32, 1910, p. 368. 
s H. W. Wiley, Prin. and Prac. of Agri. Anal.: Soils, vol. 2, 1906, p. 448. 

77 



78 FOREST PHYSIOGRAPHY 

passes at once into the vegetation, or remains in store in dry periods, or 
passes into the drainage water and is lost.^ 

It is important that the forester retain the humus of the forest soil 
and increase it or make the amounts already there more useful, since the 
nitrogen which it yields is one of the rarest of the essential plant foods 
in the soil. The maintenance of humus in the soil requires a forester's 
constant attention to renewal of growth after cutting, proper drainage, 
a shaded surface, etc.^ Different species of plants demand very different 
amounts of humus: some plants appear to require none at all, as those 
that develop on bare rock; some require a moderate amount, as is the 
case with certain grains; and others, notably the moorland plants, thrive 
only in rich humus, and have special methods of nutrition dependent 
upon the kind of soil in which they live.^ 

The great value of the birch and the aspen lies in their power of rapid 
dispersion and quick germination and growth in sterile soil or soil robbed 
of humus by repeated fires. They thus prevent excessive erosion, which 
is usually so destructive of the soil after fire has destroyed either or both 
the forest cover and the soil humus. In this manner and by their rapid 
growth they often afford an opportunity for the seedlings of longer- 
lived and more valuable trees to come in under conditions that insure 
their successful growth.* 

As an illustration of the importance of humus in maintaining an 
original growth of vegetation may be cited the fact that a change in the 
forest vegetation is known to have occurred in Denmark during past 
millennia, owing in part to the action of the wind, which by blowing leaves 
out of the forest has reduced the amount of humus. 

"When a forest soil is exposed to desiccation and the fallen leaves are carried away by wind, 
the earthworms vanish, the soil becomes dry and hard, and the vegetation suffers. In acid 
soil (bog, heath) and dune, earthworms are wanting. Upon their presence or absence depends 
the occurrence of a humus soil or a raw humus soil in north temperate forest and heath. Con- 
versely they disappear upon the production of raw humus and humous acids. Even upon the 
growth of rhizomatous plants in the forest do they exert an action; their presence or absence 
causes a series of variations in the kinds of soil that corresponds to a series of variations in 
the plants clothing it." '• 

It is noted also that a covering of leaves in a beech forest has a 
great influence upon ground vegetation in that it supports mosses and 
other plants, produces humus, and provides food for animals living in the 

1 W. J. Spillman, Renovation of Worn-out Soils, Farmers' Bull. U. S. Dept. Agri. No. 245, 
1906, p. 5. 

- E. Ebermayer, Lehre der Waldstreu, etc., 1876, p. 206. 

3 E. Warming, CEcology of Plants, Ox. ed., igog, pp. 62-64. 

■* C. S. Sargent, Manual of the Trees of North America, 1905, pp. 155-201. 

5 E. Warming, CEcology of Plants, Ox. ed. 1909, p. 78. 



HUMUS AND THE NITROGEN SUPPLY OF SOILS 79 

forest soil, among which earthworms are considered to be the most 
important.^ 

One of the most important qualities of humus that affects its value 
to the soil is its natural porosity, which renders it very absorptive of 
gases, especially aqueous vapor. Dry humus swells up when wetted 
and the volume of w^eight increases in the ratio of 2 or 8 to i; in fact 
humus stands first in this respect among the soil ingredients. 

Although in general the presence of the organic matter of plants increases the power of soils 
to hold moisture, some kinds of organic matter are known to cause a low water-holding power, 
as in certain California soils, a condition due to the peculiar and special qualities of the organic 
matter, which when extracted is found to have the properties of a varnish, repelling water to 
an extreme degree. - 

The density of natural humus as compared with ordinary soil is 
about 1:4. It is the lightest soil material and greatly promotes tilth, 
aeration, water supply, etc. Besides nitrogen, humus contains mineral 
plant food ingredients w^hich are capable of nourishing plant growth. 
These mineral ingredients are probably made available to plants largely 
through the direct and indirect action of the humus compounds; for it 
has been shown that the richer the soil is in humified organic matter 
the more rapidly the mineral matter of the soil is made available for 
plant nutrition. With an increase of soil humus there is a correspond- 
ing increase in the amount of mineral plant food extracted from the soil 
by a 4% solution of ammonia such as is employed in the Grandeau 
method of humus determination (p. 82).^ 

Organic Matter in the Soil 

The difference between soil and a mere mass of sand or disintegrated 
rock is that soil contains some organic matter. Soil becomes arable and 
furnishes a medium suitable for the growth of higher plants when a certain 
amount of organic material has been accumulated in it from the growth 
and decay of lower plants. Animal remains, such as insects and worms, 
also have a prominent place as a source of soil organic matter. The 
accumulation of the remains of micro-organisms and of the vegetation 
which they modify is an important factor in the transformation of land 
waste into soil. The final product of these and other processes is a mix- 
ture of stuff fully as complex as the processes to which it owes its origin. 

1 E. Warming, (Ecology of Plants, Ox. ed. 1909, p. 74- For a very clear and comprehensive 
discussion of the chemical modification of forest litter and its value to the soik see E. Ebermayer, 
Die gesammte Lehre der Waldstreu mit Rucksicht auf die chemische Statik des Waldbaues, 1S76. 

2 Schreiner and Shorey, Chemical Nature of Soil Organic Matter, Bull. U. S. Bur. Soils 
No. 74, 1910, pp. 8-9. 

3 E. F. Ladd, Bull. So. Dakota Agri. Exp. Station, Nos. 24-32, 35, 47. Quoted by Hil- 
gard, pp. 140-141. 



8o FOREST PHYSIOGRAPHY 

The organic matter of both plants and animals is made up of protein, 
fats, and carbohydrates principally, but besides these substances there is 
a host of other compounds such as resins, hydrocarbons, and derivatives, 
that is, alkaloids, acids, etc. Furthermore, all living matter has as 
essential components some organic compounds that contain nitrogen, 
compounds which for the most part are those related to protein. When 
the complex molecules of proteins, fats, and carbohydrates break down 
into simpler bodies they pass through the same changes whether these 
changes are brought about through the agency of micro-organisms as in 
decay or through the agency of acids; and they are subject to still fur- 
ther decomposition through the same or other agencies. The secondary 
products are very numerous and of widely varying composition and 
structure, as well as chemical and physical composition and, properties, 
so that the final products of decay are very different under different 
conditions. 

When organic matter is contributed to the soil there is a continuous 
"building-down" process from the original complex molecule to sim- 
pler ones and these again to still simpler molecules, until in some 
instances the substances are reduced to their most elementary constit- 
uents. "^ All these chemical changes are affected by the temperature of 
the soil, the amount of air it contains and the amount of water, etc. 
Dry leaves, wood, and htter generally do not change in dry air or 
change very slowly; but if the ground is moist the process goes on 
rapidly.- In the absence of air bacterial transformations cease and 
the bacteria die. Extremely high or low temperatures likewise limit 
their activities (p. 86). 

Soil Humus 

amount and derivation 

The chief source of soil nitrogen, as we have already noted, is the organic 
matter in the soil, and this occurs to a large extent in the form of "humus." 
The total amount of organic matter in ordinary soils is 2.06% for the 
soil and 0.83% for the subsoil, figures based on the analysis of thousands 
of samples from many different portions of the United States.^ There 
is an average of 28 tons of organic matter in the soil per acre taking it 
to a depth of 8 inches, and 50 tons of soil and subsoil taking it to a depth 

1 Schreiner and Shorey, The Isolation of Harmful Organic Substances from Soils, Bull. 
U. S. Bur. of Soils No. 53, igog, pp. 9-1 1. 

2 E. Ebermayer, Die gesammte Lehre der Waldstreu mit Riicksicht auf die chemische 
Statik des Waldbaues, 1876, p. 202. 

3 Schreiner and Reed, Certain Organic Constituents of Soils in Relation to Soil Fertility, 
Bull. U. S. Bur. Soils No. 47, 1907, p. 10. 



HUMUS AND THE NITROGEN SUPPLY OF SOILS 8 1 

of 2 feet.^ The amount of nitrogen is generally not far from o.i%. 
In arid soils the average amount of humus is much lower, rarely ex- 
ceeding 1% and frequently falling to or below 0.30%; but the nitrogen 
content of the humus of arid soils is very much higher than in the case 
of humid soils. Woodlands and old meadows as a rule show a high 
humus content in their surface soils. The humus content of peat and 
marshland is also high. 

While figures for the amount of humus which may be derived from a 
given quantity of vegetable matter must vary greatly according to the 
conditions under which humification takes place, it may be said that 
in the humid regions roughly one part of normal soil humus may be 
formed from five to six parts of dry plant debris. This ratio is based 
upon the assumption that the average nitrogen content of plant debris 
is 1%. The ratio will vary according to the temperature, the degree 
of access of air and moisture, etc. In hot arid regions all vegetation 
may wholly disappear by oxidation at the surface of the ground, and 
the proportion of humus derived from the decaying vegetation of arid 
regions is in general very much smaller than that of humid regions where 
it is rather rapidly incorporated in the surface soil.- 

The absolute amount of humus decreases rather regularly downward 
except in the case of depths that represent the maximum root develop- 
ment, at which level there is always a slight and often a notable in- 
crease in the humus content. Below this level decrease again takes place. 
The nitrogen percentage in the humus (which is to be distinguished 
from the total nitrogen content of the soil) exhibits a general decrease 
in the same direction, probably due to decrease in the amount of oxygen 
and a diminished rate of oxidation with increase in depth. 

The humus content of soils has a very close correspondence in some 
cases with the root development and is large in the surface layer and 
small in the subsurface layer. In other cases, while the decay of organic 
material takes place chiefly at the surface, active animal agencies may 
carry the organic remnants downward into the soil and effect a somewhat 
uniform distribution. If both root penetration and animal agencies 
are restricted by the compactness of the subsoil only a light surface 
layer of mold will be formed and what little humus is found in the lower 
soil layers will be derived entirely from the decay of a very limited 
number of roots. Cultivation or timber cutting when followed by exces- 
sive erosion prevents the accumulation of vegetable matter, from which 

1 Schreiner and Shorey, The Isolation of Harmful Organic Substances from Soils, Bull. U. S. 
Bur. Soils No. 53, 1909, p. 26. 

2 E. W. Hilgard, Soils, 1907, p. 128. 



82 FOREST PHYSIOGRAPHY 

humus is chiefly derived, and allows the too rapid aeration and destruction 
of the humus. 

In general it seems necessary to keep the nitrogen percentage of soil 
humus at about 4% to insure satisfactory results, and for the> growth of 
grasses a nitrogen percentage in the humus of 1.7% is quite inadequate, 
no matter how much humus may be present. Different plants will 
accept this minimum, as might be expected from the differences of root 
habit, water supply, lime percentage, etc., which have an influence upon 
the rate of nitrification and of the leaching of nitrogen from the soil. 

If a moderate amount of moisture is present in the soil and there is in 
consequence a relatively free circulation of the air, and if earthy carbon- 
ates are present, especially lime, so as to neutralize the acids of the 
soil as fast as formed, fungoid and bacterial growths effect the steady 
humification of organic matter. Oxygen and hydrogen are eliminated 
in the form of water and carbon dioxide, and there is an increase in the 
percentage of carbon and generally of nitrogen. When once humification 
is completed oxidation affects mainly the carbon and the hydrogen, so 
that the nitrogen content may for a time rise steadily and reach very 
high figures. Under unfavorable conditions the conversion of organic 
material to soluble nitrogen may be so slow that a soil containing as 
much as 40% of unhumified organic matter may contribute during a 
single year but a small quantity of available nitrate. 

HUMUS DEFINED 

Originally the term humus had no special significance and was only 
a name for dark-colored vegetable mold; later it came to be applied to 
this mold material when incorporated to a greater or lesser degree in 
soils. The term now has a more restricted meaning, at least among 
soil chemists, and is applied exclusively to the dark-colored organic 
matter extracted from soils by dilute solutions (usually 5% solutions) 
of sodium or ammonium hydrate.^ The method of determination is 
purely empirical and ascertains the existence of only a portion of the 
organic matter of the soil. 

Among agricultural folk and in general among foresters the term 
humus still retains its early meaning — -partly decomposed organic 
material, dark in color, light in weight, and mixed with more or less 
mineral matter. 

The amount of humus in the soil is sometimes determined by means of dry or wet combustion 
in which process the humus is calculated from the carbon dioxide formed and the nitrogen 
gas is measured directly. Obviously this measurement includes the entire organic matter of 

1 Methods of Analysis, Humus in Soil, Bull. U. S. Bur. Chem. No. 107, 1907, p. 19; see 
also C. A. Davis, Peat, 8th Ann. Rept. Mich. Geol. Surv., igo6. 



HUMUS AND THE NITROGEN SUPPLY OF SOILS 



83 



the soil whether humified or unhumified. To obtain the amount of actual functional humus 
in the soil (only humified organic matter can be directly nitrified) a solvent must be employed 
and discrimination between humified and unhumified material made. The accepted process 
is the method of Grandeau. By this method the soil is first extracted with dilute acid in order 
to set the humic substances free from their combinations of lime and magnesia and a subse- 
quent extraction is made with moderately dilute solutions of ammonia. After the evaporation 
of the ammonia solution the humus is left behind in the form of a black substance somewhat 
resembling soot. This is then weighed and afterwards burned and the ash weighed. The 
amount of functional humus is considered to be the difference between these two weights. 
The nitrogen content of the humus may be determined directly by substituting in this process 
potash or soda lye for ammonia water and determining the nitrogen by the Kjeldahl method in 
the filtrate. 1 

The chemical composition of humus is indefinite because it itself is 
a variable mixture of substances of complex composition. It always 
contains more carbon and nitrogen and less oxygen and hydrogen than 
the substances from which it was formed. The following table shows 
the chemical composition of grass and of the top brown layer of turf 
in a peat bog, also the composition of peat of greater age, at 7 feet 
and 14 feet respectively. 

CHEMICAL COMPOSITION OF VARIOUS TYPES OF ORGANIC MATTER.^ 





Grass < Top Turf 


Peat at 7' Peat at 14' 


Carbon 

Hydrogen 

Oxygen 

Nitrogen 


SO. 3 
5-5 

42.3 
1.8 


57.8 
5.4 

36 
0.8 


62 

5.2 
30.7 

2. I 


64 

S 
26.8 

4-1 



It should be remembered in the inspection of this table as well 
as in the general consideration of humus that vegetable matter con- 
sists, in addition to carbohydrates, of other carbon compounds con- 
taining nitrogen, and in some cases both nitrogen and phosphorus, 
which all break down under bacterial and acid action into dark-colored 
substances called humus. In the process of humus formation the 
nitrogen-containing bodies resist the action of bacteria longer than the 
carbohydrates, so that the later the stage of decay the greater the pro- 
portion of nitrogen the humus will carry. It follows that during the 
gradual depletion of the humus higher and higher percentages of nitro- 
gen will be developed in that part not removed.'^ 

Humin and humic acid are terms used in designating vegetable acids 
resulting from the decay of vegetable matter in the formation of peat, 
etc. The descriptions and formulae for humic acid and related bodies 

1 For a description of the Kjeldahl method see Wiley, Soils, 1906, p. 491 et seq. 

2 A. D. Hall, The Soil, 1907, P- 42. 
' Idem, pp. 41-44- 



84 FOREST PHYSIOGRAPHY 

are about as numerous as the number of investigators.^ Certain elabo- 
rate experiments have resulted in the attempt to show that humic acid 
consists for the most part of an insoluble body of a protein nature, but 
this proves only that the humic acid examined by this investigator was 
either of a protein nature, a mixture of protein decomposition products, 
or probably both, together with some unknown body.- 

Humic acid, ulmic acid, ulmin, etc., are commonly used as if they were definite bodies of 
well-established composition, but this is not the case, as their very existence has never been 
satisfactorily demonstrated. Ne attempt should be made to ascribe formulas to acids of so 
complex and variable a nature. As commonly written the formulae for the group are as follows: ' 

Ulmin and Ulmic Acid 

Carbon 67.1%] 

Hydrogen 4.2 > Corresponding to C40H28O12 + H2O 

Oxygen 8.7 J 

HuMiN AND Humic Acid 

Carbon 64 . 4% 1 

Hydrogen 4.3 > Corresponding to C2iH240i2-t- 3 H2O 

Oxygen 31.3 J 



Crenic Acid 

Carbon 44 . 0% 

Hydrogen S . S 

Nitrogen 3.9 

Oxygen 46 . 6 



Corresponding to C12H12O8 ? 



Apocrenic Acid 
Carbon 34.4%! 

^yf^'^Sen 3.5 Corresponding to C24H24O12 ? 

Nitrogen 3.0 

Oxygen 39.1 J 

The ulmic, crenic, and apocrenic acid groups are therefore names for 
exceedingly complex and unstable compounds as yet but very little 
understood. Although they have never been isolated and their char- 
acter definitely determined it should be remembered that there is reason 
for believing that they have at least a very short-lived existence in the 
soil. If they exist at all they pass quickly into the higher stages of oxi- 
dation and their final condition is CO2; yet it is believed that during 
their supposed brief existence they may not only attack alkalies and 
alkali earths but also dissolve even silica.^ 

Clarke asserts that they have a very appreciable solvent power and advance the decompo- 
sition of rocks, but notes that their constitution is but little understood. * 

1 Schreiner and Reed, Certain Organic Constituents of Soils in Relation to Soil Fertilitj', 
Bull. U. S. Bur. of Soils No. 47, 1907, pp. 14-16. 

2 Suzuki, Bull. Col. Agri. Tokio, vol. 7, 1907, p. 513. Quoted by Schreiner and Shorey in 
Bull. U. S. Bur. of Soils No. 53, p. 19. 

' G. P. Merrill, Rocks, Rock-weathering and Soils, 1896, pp. 189-199. 

* Sir Archibald Geikie, Text-book of Geology, 3d. ed., 1886, p. 472. 

5 F. W. Clarke, The Data of Geochemistry, Bull. U. S. Geol. Surv. No. 330, 1908, p. 409. 



HUMUS AND THE NITROGEN SUPPLY OF SOILS 85 

Hilgard says that an acid reaction is characteristic of the soils of many woodlands, as is 
notable of the soils of the long leaf pine region of the South as well as of many deciduous forests 
in northern climates. He believes that in the course of time oxidation converts the natural 
neutral humin and ulmin into humic and ulmic acids capable of combining with the bases. 
Still further action is thought to result in the formation of crenic and apocrenic acids, which are 
readily soluble in water and in part form soluble salts with lime, magnesia, and other bases. 

"These acids act strongly upon the more readily decomposable silicates of the soil, and in 
the course of time may dissolve out, and aid in the removal, by leaching, of most of the plant- 
food ingredients ... of the soil."' 

It is conceived that this agency may be responsible for the almost complete absence of 
mineral plant food in the lower portions of peat beds and the subclays of coal beds. 

Besides the uncertain humus compounds of ulmic, humic, crenic, 
and apocrenic acids, there are others of similar derivation the action 
of which is not yet understood; among them are xylic acid, saccharic 
acid, and glucinic acid, and a black humus acid containing 71.5% of 
carbon and 5.8% of hydrogen. 

In the old forests of northern climates there is sometimes formed at the 
surface a partially decomposed peaty layer or vegetable remains which 
retards the full production of the land both while occupied by forests 
and for some time after being cleared.^ In the case of such arrested 
humus development the soil becomes sour. The sourness is thought to 
be due to the presence of the above-named acids. 

Raw humus or unhumified organic material consists of incompletely 
decomposed plant remains, and may be found so rich in such remains 
from 50% to 60% organic matter as to be employed as fuel. It has 
free vegetable acids in abundance, earthworms can not penetrate it, and 
by itself it is of no value to plants. Raw humus appears in the forest 
in poorly drained places or in places exposed to wind, while ordinary 
humus with its earthworms, insects, etc., occurs in fresh, sheltered places. 
Ordinary humus or vegetable mold contains many fungi, besides earth- 
worms and insects, and is an excellent nutritive substance for plants: 
the rapid production of humus in the forest is therefore a kind of 
natural manuring. When ordinary humus in the beech forests of 
Europe is displaced by raw humus because of timber falls, etc., the beech 
is no longer capable of regeneration and disappears, being replaced by 
a heath.^ 

Unhumified organic material has a potential value through the pos- 
sibility of its nitrification into active humus. It also lightens the soil 
by rendering it more pervious to air and water, and by progressive decay 
gives off carbon dioxide, which is the basis of carbonic acid so important 
in soil decomposition. 

1 E. W. Hilgard, Soils, 1907, p. 126. 
' Muller, NatiirHche Humusformen. 
' E. Warming, (Ecology of Plants, Ox. ed., 1909, pp. 62-63. 



86 FOREST PHYSIOGRAPHY 

ACTION OF BACTERIA 

We have as yet only briefly mentioned the action of bacteria in rela- 
tion to soil nitrogen. Further discussion is required in order that the 
conclusions concerning the control of bacterial action may be adequately 
understood. Since the growth of bacteria is a large factor in maintain- 
ing the supply of some of the most important plant foods, the conditions 
which promote the activity of such bacteria are matters of serious interest 
to those engaged in the production and care of plants. 

Bacteria are plants that form the simplest group of fungi and are lacking in chlorophyll. 
They are very minute. The largest forms may reach a diameter of 0.008 mm. (0.000352 
inch), and the majority are not more than 0.005 mm. (0.000197 inch) in diameter. It is 
believed that some bacteria are too small to be seen even with the most powerful microscope. 
Though they are of small size they are concerned with almost every phase of our daily life and 
overcome their apparent insignificance by their incredible numbers and ceaseless activity. A 
fertile soil has from 500,000 to 10 million bacteria to the gram, or from 15 million to 300 million 
to the ounce.' In a drop culture of one cubic millimeter an experimenter found that one-tenth 
the total volume was composed of bacteria. In 24 hours, 48 generations will produce 281,500 
billions of organisms.- They are most numerous near though generally not at the surface, de- 
crease in numbers rapidly downward, and generally vanish at seven or eight feet. Water drawn 
from deep wells does not show any bacterial growth. 

The functions and value of soil bacteria are variable, but the kinds 
that thrive in the soil are chiefly beneficial. Their action in the soil 
is affected by moisture, temperature, degree of comminution of soil 
particles, aeration, drainage, etc., besides which bacteria have associa- 
tive relations with each other whose reactions may be either bene- 
ficial or harmful. Some of them decompose dead plant and animal 
matter into simpler compounds, reconstruct various inert materials, 
and thus constantly renew certain elements in the soil and maintain its 
fertility. It should be remembered, however, that if the conditions of 
food supply and environment are unfavorable harmful groups of bac- 
teria may destroy the fertility of the soil.^ 

Humus is essentially a product of bacterial action, but this action 
should be carefully distinguished from the later action, called nitri- 
fication, which transforms the nitrogen of the humus into available 
nitrates. The formation of humus is accomplished mainly by the 
breaking down of carbon compounds, especially the carbohydrates of 
plant tissues, with the production of marsh gas or hydrogen, carbonic 
acid, and humus. With a surplus of air the humus-forming fermenta- 

1 K. F. Kellermann, The Functions and Value of Soil Bacteria, Yearbook U. S. Dept. 
Agri., 1909, pp. 219-226. 

2 Grandeau, Ann. Sci. Agr., vol. 1905, p. 456. 

« For Winogradsky's classification of nitrifying organisms see H. W. Wiley, Prin. and Prac. 
of Agri. Anal.: Soils, vol. i, 1906, p. 557. 



HUMUS AND THE NITROGEN SUPPLY OF SOILS 87 

tion is replaced by one which results in the complete combustion of the 
organic matter to carbonic acid. It is largely for this reason that more 
humus is found in a pasture or a forest than in a continuously tilled field. 

Most aerobic (oxygen-consuming) bacteria require for their well- 
being, or even in some cases their existence, some carbon compounds of 
nitrogen, and will begin to break down proteids and other nitrogen-con- 
taining materials. The products of their action, Fig. 9, are successively 
peptones (like leucin and tyrosin), eventually ammonia, and probably 
free nitrogen, but the formation of ammonia is the most characteristic 
effect of the bacterial fermentation of a proteid. When organic matter 
has decayed to the stage of such simple compounds as ammonia, nitric 
acid, carbonic acid, etc., it is no longer organic matter and much of it 
may escape from the soil altogether.'^ 

Ammonia is not directly assimilable in the soil when delivered to it by 
the air or when occurring as the product of plant decay. The ammonia 
of air and soil is converted into nitrous acid by bacteria or by the oxi- 
dation produced under the influence of the catalytic activity of ferric 
hydroxide. The latter process takes place at a temperature of 15° to 
25° C, and under its influence a certain amount of available nitrogen is 
developed in the soil independently of the activity of the nitrifying fer- 
ments. The conversion of ammonia into nitrates is, however, chiefly 
accomplished by two groups of organisms, (i) nitrosomonas or nitro- 
sococcus and (2) nitrobacteria. The action of the first group is limited 
to the formation of a nitrite; the action of the second group is the oxi- 
dation of the nitrite to a nitrate. Both groups are active only upon 
humus and its products, and are to be distinguished from the ammoniacal 
bacteria (such as Bacillus mycoides) that effect the reduction of the 
carbohydrates and the oxidation of proteid compounds to humus and 
ammonia. The latter have wholly different habits. In general the nitri- 
fying organisms require both organic and mineral substances for proper 
growth. Indeed some forms of nitrifying organisms have the power of 
subsisting wholly upon mineral substances." 

The proper conditions for both groups of organisms are somewhat 
definite. A fairly high temperature, 75° F., is most favorable, and there 
must be a certain amount but not an excess of moisture present in the 
soil. If the temperature is low and water is present in excess, bacterial 
action may be incomplete in its effects or cease altogether. This is 
illustrated by the preservation of leaves, stems, and seeds for thousands of 

1 Schreiner and Shorey, Chemical Nature of Soil Organic Matter, Bull. U. S. Bur. Soils 
No. 74, 1910, p. 45. 

2 H. W. Wiley, Prin. and Prac. of Agri. Anal.: Soils, 1906, pp. 522-526 at al. 



88 FOREST PHYSIOGRAPHY 

years in peat bogs, and by the well-known antiseptic properties of sour 
humus or peat. Free oxygen in large quantities is required, and there 
must be present a base or its carbonate, such as lime, with which the 
acids due to oxidation immediately unite. Sour soils exclude nitrify- 
ing bacteria through the action of the organic acids that have not been 
neutralized. 

The neutralizing salts favorable to bacterial development are not restricted to the carbonates. 
Potassium chloride acts favorably up to 0.3% but suppresses nitrification at 0.8%. Earthy and 
alkahne sulphates act favorably up to 0.5%. Among the latter gypsum is most beneficial and 
accelerates the process more than any other substance known. Common salt inhibits nitrifica- 
tion to a notable degree, and to this fact is due in great part the absence of nitrates in low- 
lying seacoast tracts. Arranged in the order of their value to the nitrifying process the various 
substances stand as follows, taking gypsum at 100% (after Pichard). 

Gypsum 100% 

Sodic sulphate 47-9 

Potassic sulphate 35-8 

Calcic carbonate i3-3 

Magnesic carbonate 12.5 

The value of thorough aeration in nitrification is shown by the experi- 
ments of Deherain in which a cubic meter of soil was left undisturbed 
for several months while a similar mass was agitated in air once a week 
for the same period. At the end of the experiment it was found that 
the ratio of nitrogen content in the two samples was i : 70 respectively.^ 
It has also been shown- that the brown substances of humus and analo- 
gous compounds are directly oxidized to some extent under the influence 
of air and sunlight, thus forming carbonic acid. The process is purely 
chemical, has no relation whatever to bacteria, and is rendered more 
effective by cultivation, principally through the better aeration thus 
effected. The succession of changes through which organic matter 
passes in the processes of nitrification and denitrification is shown in 
the accompanying diagram. Fig. 9. It presents in summary form the 
principal changes that have thus far been described. 

The immensely important conclusion has recently been established 
that all soils contain groups of protozoa which feed upon living bacteria 
and restrict their numbers, thus acting as beasts of prey.^ Their preda- 
tory activities seriously restrict the limits of nitrogen production even ■ 
when the amount of organic matter in the soil is greatly increased. 
Happily a remedy has been found in heating or in treatment with anti- 
septics. Crop increases of 30% have been effected by a 48-hour treat- 

1 E. W. Hilgard, Soils, 1907, p. 147. 

2 Berthelot and Andre, Comptes Rendus Academie de Paris, 114, i8g2, pp. 41-43. 
s A. D. Hall, The Fertility of the Soil, Science, n. s., vol. 32, 1910, pp. 370-371. 



HUMUS AND THE NITROGEN SUPPLY OF SOILS 



89 




Fig. 9. — Diagram indicating the nitrogen changes in 'the soil produced by the action of bacteria. The 
arrows indicate the course of the changes which various groups of bacteria may produce in the nitrogen 
compounds of the soil. A, action of ammonifying bacteria which change organic nitrogen to ammonia; 
B, action of nitrifying bacteria which change ammonia to nitrite; C, action of nitrifying bacteria which 
change nitrite to nitrate; D, assimilation of nitrate by green plants; E, action of denitrifying bacteria 
which change nitrate to nitrite; F, action of denitrifying bacteria which change nitrite to ammonia; 
G, action of denitrifying bacteria which change ammonia to nitrogen gas; H, action of bacteria which 
change nitrogen gas into proteid nitrogen; I, action of bacteria which in symbiosis with leguminous 
plants change nitrogen gas into proteid nitrogen; K, action of bacteria which in symbiosis with certain 
non-leguminous plants change nitrogen gas into proteid nitrogen.' 

1 Yearbook, Dept. Agri., 1909, p. 222. 



90 FOREST PHYSIOGRAPHY 

ment of the soil with vapors of toluene, chloroform, etc., followed by 
complete volatilization of these antiseptics. Analyses of the plant 
material so produced shows an assimilation of greater amounts of other 
plant foods as well as of nitrogen. It follows that the extra growth 
does not represent mere temporary stimulation but an absolute increase 
in the available stores of plant food. While great numbers of bacteria 
also succumb in the application of the remedial measures, some of them 
escape, and these, immune from attack, increase at a prodigious rate 
and almost at once increase the soil fertility.^ 

Several species of bacteria have the power of direct fixation of nitro- 
gen from the soil air. Some of the most important of these bacteria 
are Clostridium pasteurianum, Bacillus alcaligenes, Bacillus tumescens, 
Pseudonionas radicicola, Granulobacter and several species of Azoto- 
bacter.'^ The abundance of these bacteria in the soil seems to indicate 
the measure of the natural nitrogen-recuperative power of the soil. In 
the coastal-plain soils the genus Azotobacter occurs only in the surface 
layer of a few inches; in the deep and almost exhaustless soils of certain 
sections of the West the same genus is found in active condition even 
down in the fifth foot below the surface. While most investigators 
attach considerable importance to the direct fixation of nitrogen, Hall 
considers that it is yet to be ascertained if the direct fixation of nitrogen 
by bacteria has any very important part in re-creating the store of 
uncombined nitrogen in the soil.^ 

An interesting and elaborate series of experiments by Lipman* makes 
it seem likely that Azotobacter chroococcum has the power of fixing 
atmospheric nitrogen when in symbiotic association with certain green 
algae with which it is commonly found and which develop with great 
rapidity upon limestone soils. It has also been shown by Lipman that 
Azotobacter vinelandii does not require symbiosis with algae to fix 
atmospheric nitrogen, but that a mixture of it and another bacillus 
(No. 30) caused a doubling of the nitrogen development. 

Certain bacteria have nitrogen-fixing power when in symbiotic asso- 
ciation with various legumes such as clover, etc., and accumulate large 
amounts of soluble nitrates which are ultimately used by the host plant. 

1 There are also present in the soil anaerobic or denitrifying bacteria whose life functions are 
not dependent upon the presence of air since they are able to avail themselves of combined 
oxygen by reducing the oxides present in the soils. Some of them cause the reduction of nitrates 
to nitrites and finally to ammonia as shown in Fig. 9. Such reductive processes are carried 
on by bacillus denitrificans I, and occur chiefly in soils rich in organic matter or badly aerated. 
The result is a loss of nitrogen and a depletion of the plant food in the soil. 

^ Yearbook Dept. Agri., 1909, p. 225. 

3 A. D. Hall, The Soil, 1907, p. 171. 

< Rept. Agri. E.xp. Station, New Jersey, 1903-1904. 



HUMUS AND THE NITROGEN SUPPLY OF SOILS 



91 








Fig. 10. — Upper figure represents nitrous ferment prepared by Winogvodsky from soil from Cite 
Lower figure represents nitric ferment from the same source. (Wiley Soils.) 



92 FOREST PHYSIOGRAPHY 

The bacteria live as parasites within the roots of the host plant from 
which they derive their carbohydrate food supply. The presence of 
the parasites stimulates the development, by the root, of the peculiar 
swellings known as root nodules or root tubercles. These become 
filled with a bacterial mass consisting principally of swollen and ab- 
normal (hypertrophied) "Bacteroids" having forked outlines, but in 
part also of bacteria which remained in their normal condition.^ For 
a time the nodule increases in size and the bacteria continue to furnish 
a steady supply of nitrogenous material to the host plant. Ultimately 
the nodules cease growing, the Bacteroids degenerate, and their sub- 
stance is absorbed by the host. Normal bacteria, however, remain 
and provide for future reproductions. 

When the root nodules cease growing the larger group of bacteria, 
called also bacteroids, gradually collapse and are then depleted of their 
nitrogenous substance. The bacteria capable of this action dravv^ their 
supply of food largely from the plant with which they grow in sym- 
biotic relationship. It follows also that when the plant becomes sea- 
sonably inactive the bacteroids also become inactive for a season; they 
are found only upon actively growing roots and not upon the roots of 
dead legumes. 

A fourth process of nitrogen fixation is by symbiosis, in which the plant involved is one 
other than a legume. Whether this process has any practical value remains to be determined, 
but bacterial nodules have been found upon at least one species of Alnus (alder), upon Ceano- 
thtis americanus (red root, New Jersey tea), Ceanothus velnlinus, Elaeognus argenlea (silvery 
heriy), Shepherdia argettlea (buffalo berry or rabbit berry), Podocarpus macrophylla, and several 
genera of the cycads, though the nodules of the latter group of plants are quite different in some 
ways from the nodules of legumes.^ 

One investigator concludes that the property of utilizing atmospheric 
nitrogen belongs to many other plants than the legumes.^ He contends 
that in all the plants examined by him structures were found which are 
capable of absorbing it from the air and transforming it into the organic 
state. . The chlorophyll cell seems to possess this power to a high degree. 
It absorbs free nitrogen and transforms it into organic compounds. 
Certain organs, called producers of nitrogen, occur in the tender parts 
of very young leaves or their petioles. But the whole matter of such 
utilization by non-leguminous plants requires much further work before 
these broad conclusions can be accepted. 

1 Sharburger, Noll, Shenck, and Karsten. A Text-book of Botany, 3d Engl, ed., 1908, p. 232. 

2 K. F. Kellermann, The Functions and Value of Soil Bacteria, Yearbook Dept. Agri., 
1909, p. 226. 

3 Jamieson, Rept. Agri. Research Assn. of the Northeastern Counties of Scotland, 1905, 
p. 16. 



HUMUS AND THE NITROGEN SUPPLY OF SOILS 93 

It has been fairly well demonstrated that forests are able to appro- 
priate free nitrogen by means of their trichomes.^ In a large number 
of chemical tests conducted in such a manner as, it is believed, to exclude 
all other sources of nitrogen than the atmosphere it was found that nitro- 
gen is always present in the trichomes. Among the forest trees that 
have been tested are Acer campestre, Tilia europaea, Ulmus campestriSy 
Sorhus Aucuparia, Fagus sihatica, and Ahies concolor. The process is one 
of unusual interest, for it adds one more to the very brief list of means 
by which nitrogen is made available as a plant food. This statement 
should not be taken to indicate that plants in general are capable of 
fixing nitrogen. The experiments of two Rothamsted (England) inves- 
tigators, Lawes and Gilbert, and of Boussingault in the middle of the 
nineteenth century are very conclusive in their determination of the 
inability of cultivated plants to fix atmospheric nitrogen except in 
symbiosis with nitrogen-fixing bacteria.^ The decay of forest litter and 
its transformation into nitrates by bacterial means are the chief processes 
that supply nitrogen in forested areas.^ 

ACTION OF FUNGI 

Contributing to the general store of humus in the soil are a large 
number of fungi among which are Penicillium, Mucor, Aspergillus, 
Oidium, etc.^ They take a prominent part in the conversion of vege- 
table matter into black neutral insoluble humus, a process that is always 
marked by the formation of carbon dioxide. It is always found that 
both the fungous tissues and the humus resulting from their decay are 
notably richer in nitrogen and carbon than the higher plants. These 
organisms are found about decaying roots and plants, though they are 
not confined to this occurrence. Their tiny fibrils or hyphae are scattered 
through the ground much more thoroughly than even the tiniest root- 
lets with which they are associated. It is this thorough distribution 
that makes their presence so important in soil fertility, for it results 
in a correspondingly wide dissemination of the humus to which the 
fibrils contribute. Their life functions are dependent upon air, so that 
thorough aeration promotes their activity and increases their number; 
it follows that they will be most numerous near the surface and that 

1 T. Cleveland, Jr., Forests as Gatherers of Nitrogen, Science, n. s., vol. 31, 1910, p. 908. 

2 A. D. Hall, The Soil, 1907, p. 162. 

3 Warming suggests mutual reactions between plants as possible sources of nitrogen. 
"Experience has shown that where Picea excelsa has been planted in Jutland it flourishes 
better in company with Finns montaiia than without it. It is probable that in this case the 
mountain pine provides the spruce with nitrogen." 

i A. D. Hall, The Soil, 1907, p. 182. 



94 FOREST PHYSIOGRAPHY 

the nature of the soil drainage will determine their maximum depth or 
even their very existence. 

From the standpoint of the forest it is fortunate that these growths 
are not confined to decaying vegetation. They infest the roots of a 
large number of trees and shrubs and enable the latter to assimilate 
indirectly the decaying organic and inorganic matter that would other- 
wise be unavailable. They are in symbiotic association or cooperation 
with pines, firs, beeches, aspens, and many other forms, all of which 
appear to depend very largely for their healthy development upon 
such association.^ The degree of dependence of the host plant upon 
the fungoids that inhabit it is emphasized by Frank, who says that 
some host plants are so dependent upon this relation to obtain the 
necessary carbon from the humus that they possess no green carbon- 
assimilating foliage, a condition illustrated by the Neottia nidusavis 
or Bird's-Nest Orchid found among beech underwood in England. 
The action requires close association of host plant and fungus, and in 
some cases the fungus penetrates the cortical tissue of the root or forms 
a sort of cap on the ends of the smallest and shortest rootlets.^ The 
association, when it results in the supplying of the host plant with 
mineral substances, is especially characteristic of plants that grow in 
soils subject to drought or poor in mineral salts or rich in humus. In 
general those plants that have feeble transpiration capacity are well 
supplied about their roots with fungus through which they obtain food 
of many kinds from the soil. Such plants have also a very limited 
starch development in the leaf. Fungi may be harmful in their action 
when they rapidly transform the plant food into available form and 
produce such large amounts as to cause the excess to be removed by 
solution, so that a luxuriant but short-lived growth occurs, as in the 
"faery rings" common in poor pastures.^ 

1 E. W. Hilgard, Soils, 1907, p. 157. 

2 A. D. Hall, The Soil, 1907, p. 183. 

3 Idem, pp. 184-185 and 219. 



CHAPTER VII 

SOILS OF ARID REGIONS 

General Qualities 

The rainfall of arid regions is insufficient to leach out of the soil the 
salts that tend to form in it during the progressive weathering of the 
rock. In humid regions where the rainfall is abundant these salts are 
leached out and pass in very dilute form through springs and streams 
into the sea, and relatively small portions of the salts formed by weath- 
ering are retained in the soil and utilized by plants. It follows that when 
the degree of aridity is variable the salt of the soil will be variable in 
kind and amount and that in extremely arid regions practically the 
entire mass of salts contained in the rocks remains in the soil. 

We have already seen that arid soils are potentially more fertile than 
humid soils, for abundant rainfall in the latter case leaches the soil of 
valuable fertilizing elements that are easily soluble. In arid regions 
these elements are retained in the soil and many of them are very pro- 
ductive. To this advantage is added the greater number of bright 
clear days in arid regions and a maximum of insolation. The favorable 
features of arid soils are illustrated by the bench lands about San 
Bernardino, which are fertile, warm, equable in temperature, free from 
alkalinity, and, where water can be directed upon them for irrigation, 
among the most valuable agricultural lands in the United States.^ 

The most striking characteristic of the soils of arid regions is the 
uniformly high percentage of lime and, as a rule, of magnesia, no matter 
what the underlying geologic formations happen to be. This condition 
is all the more apparent in the United States because of the general 
absence of limestone formations in the more arid portion of the country 
west of the Rocky Mountains and the wide distribution of such forma- 
tions east of the Rocky Mountains. No matter what the formation 
is, whether it is the granite of the Sierra Nevada foothills, the eruptives 
of the coast ranges of California and Oregon, or the great basalt sheets 
of Idaho and Washington, they are all alike in producing soils with a 
high lime content. 

It is largely to the high percentage of lime that the flocculated condi- 
tion of arid soils is due. This is one of their notable characteristics, 

I W. C. Mendenhall, The Hydrology of San Bernardino Valley, Cat, Water-Supply Paper, 
U. S. Gaol. Surv. No. 142, 1905, p. 17. 

95 



96 FOREST PHYSIOGRAPHY 

and is related to the great depth of root penetration and easy tillage in 
arid lands. 

While in humid regions the average nitrogen content of soil humus 
is less than 5%, in the upland soils of arid regions the percentage rises 
as high as 22%, with a general average between 15% and 16%. This 
is probably due both to the presence of the lime which keeps the 
acids that tend to form in the soil completely neutralized, and to the 
deficiency of vegetable matter which allows more complete nitrification 
than when an excess of such matter is present. The absence of an abun- 
dance of vegetable matter in the surface soil and of other qualities that 
differentiate it from the subsoil is a distinguishing character of arid- 
region soils. Subsoil and surface soil have no sharp line of separation 
either in fertihty or general appearance or composition. The decom- 
posed state of arid subsoils, the absence of that rawness that character- 
izes humid subsoils, and the possibilities of their utilization are shown 
by the manner in which quick growths of yellow pine {Pinus ponderosa) 
appear in the placer mines of the foothills of the Sierra Nevada of 
California where the subsoil was thrown out years ago and became the 
surface soil. The timber growth is now of sufficient size to be used for 
mine timber and a second young forest is springing up on the red earth 
which once appeared as barren as the desert.^ 

In the case of the relatively insoluble ingredients of the soil such as 
quartz or silica, the substance making up the greater part of sand, the 
humid region contains the larger amount, 84%, as compared with the 
69% of the arid region where other substances exist in greater pro- 
portions. So that while sand of humid regions ordinarily consists of 
a collection of quartz grains with relatively clean surfaces, in arid 
regions it consists of a great variety of minerals in a partially decom- 
posed condition. Mixtures of fine and coarse particles at the surface 
are also more common in arid than in humid soils, due to the absence 
of thorough sorting in water. Thus the soils of arid regions often have 
uniform physical and chemical characters to a great depth. 

Scantiness of rainfall in arid regions effects a great retardation in 
the rate at which clay forms from feldspathic rocks and the sediments 
derived from them. This is shown in the distribution of two broadly 
different soil types in the eastern wet and western dry portions of the 
country. The soils of the Atlantic slope are prevalently loams and con- 
tain considerable clay; the soils of the arid region are generally sandy 
or silty with a small amount of clay unless derived directly or indirectly 
from clay or clay shales. 

1 E. W. Hilgard, Soils, 1907. 



SOILS OF ARID REGIONS 97 

The amount of phosphoric acid contained in the soils of arid regions 
is not different from that contained in the soils of humid regions. 
Phosphorus is a substance tenaciously retained by all soils and appears 
to be independent of leaching. On the other hand the leaching process 
has such a marked influence upon the compounds of the alkaline metals, 
potassium and sodium, which are readily soluble in water, that the 
ratios of their percentages show a marked difference in humid and in 
arid regions. The average ratio for potash is .216% to .672%, the. 
ratio for soda is .140% to .420%. Potash occurs in greater abun- 
dance than soda in all soils because it is tenaciously held through 
reactions effected by zeolitic compounds in which soda is wholly or 
partially displaced when brought into solution with a potash compound, 
so that soda accumulates only where the rainfall or drainage is in- 
sufl&cient to effect proper leaching; in such places it results in what is 
generally known as an alkali soil. Potash is therefore relatively abun- 
dant in arid soils and is one of the last substances added to them for 
increasing their productivity. They rarely contain much less than 1% 
of acid-soluble potash, occasionally rising as high as 1.8%. 

Among the most notable differences in the composition of arid and 
humid soils is not only the smaller amount of humus found in arid 
regions but also the relatively higher nitrogen content of the arid-soil 
humus. On the average, the humus of arid soils contains about ^}^ 
times as much nitrogen as the humus of normal soils and in extreme 
cases the amount may be 6 times as great, in which case the nitrogen 
percentage in the arid humus considerably exceeds that of the albu- 
minoid group, so that in arid regions a humus percentage which in 
humid regions would be considered quite inadequate may be considered 
entirely sufficient for all crop demands.^ In arid regions the substance 
that first requires replacement is phosphoric acid, the second is nitrogen. 

Alkali Soils 
For reasons already stated in connection with the higher percentage 
of soluble salts in arid regions, certain tracts may under special topo- 
graphic and drainage conditions develop alkalinity, a condition due to 
the presence of three compounds which usually form the main mass of 
the salts — the sulphate, chloride, and carbonate of sodium. .Among 
these, calcium sulphate is nearly always present, magnesium sulphate 
(Epsom salt) is in many cases very abundant, and calcium chloride 
is present occasionally. The composition of a more or less typical 
alkali soil in California is shown in the subjoined table. ^ 

1 E. W. Hilgard, Soils, 1907, p. 138. 

2 Hilgard and Weber, Bull. Cal. Agri. Ex. Sta. No. 82, p. 4. Quoted by Wiley. 



98 FOREST PHYSIOGRAPHY 

TABLE SHOWING COMPOSITION OF ALKALI SALTS IN SAN JOAQUIN VALLEY 





Tulare County 




Goshen 


People's 
Ditch 


Near 
Lake 
Tulare 


Visalia 


Lemoore 


Tulare 
Expm't 
Station 




Surface 
Soil 


Alkali 
Crust 


Surface 
Soil 


Surface 
Soil 


Alkali 
Crust 


Alkali 
Crust 




1.40 




0.83 


1.26 


































18.80 
13-4 
45-3 
4-4 
10.4 






Sodium sulphate (Glauber's salt) 


44.24 

32. g8 

16.74 

i.gy 


1.22 

88.09 

1 .00 


3i-3oW 
18.2 

0.22 


chiefly 


32.8 


Sodium chloride {common salt) 

a Sodium phosphate 


little 


31-16 


little 
moderate 












8.1 






1.97 


9.21 


7-S 













a Very generally present, but not always in quantities sufScient for determination. 

Alkali lands are so widely distributed in the desert regions of the 
world ^ that the problem of their improvement and utilization for agri- 
culture is of great importance. These lands when properly treated have 
great fertility on account of the many soluble plant foods in them, and 
they may in many places be turned from waste lands to fertile oases. 
Their natural vegetation is of little value except in a few cases, as the 
salt bushes and wild clover of South America and Australia, which form 
valuable pasture. Considerable areas of alkali lands are either destitute 
of vegetation or bear resistant growths of little value as forage. The 
effects of sodic carbonate on plants grown in alkaline regions are seen 
in a scant leafage, short growth of shoots, and a deadening of the roots. 
The cortex assumes a brownish tinge just above the surface in the case 
of green herbaceous stems, and, in the case of trees, the outer bark 
assumes an almost black tint and the green layer underneath turns 
brown. The maximum injury is usually at or near the surface, where 
there is a maximum accumulation of salts, due to evaporation at the 
surface. The vertical distribution of the alkali salts in a California soil 
is shown in the diagram below. Fig. ii.- 

Certain native plants that live upon alkali soils have adapted their 
root systems to a very interesting condition. Figure 11 shows that down 
to a depth of 15 inches there is practically no alkaline content; and it is 
within these 15 inches of soil that the native plants develop their roots 

1 The total area of the arid lands of the world computed from the total area of interior basin 
drainage is given by Sir John Murray as 11^2 niillion square miles, or one-fifth of the total land 
surface of the globe — The Origin and Character of the Sahara, Science, vol. 16, 1890, p. 106. 

2 E. W. Hilgard, Soils, 1907, p. 432. 



SOILS OF ARID REGIONS 



99 



and develop their growth. The bulk of the salts accumulate at the 
greatest depth to which the annual rainfall of seven inches reaches, where 
it forms a hardpan. It is above this hardpan that the seeds of the 
shallow-rooted plants germinate and extend their roots. The soil mois- 
ture of the surface layer is so thoroughly consumed by the plants that 
no alkah is brought up from below by evaporation and the life cycle 
begins the following season. It is in this manner that the luxuriant 
vegetation of the San Joaquin plains is maintained except where occa- 
sional alkaline spots occur. The horizontal distribution of alkah is 
variable and the location of the salts changes from year to year, espe- 
cially in irrigated lands, so that the cultivation of alkah lands, the de- 
termination of their position, etc., must be carried on with great care. 



Amounts of Ingredients in 100 of Soil 1 
.02 .01 .06 .08 .10 .12 .14 .16 .18 .20 .22 .24 .26 .28 .30 .32 .34 .36 .38 .40 .42 .44 .46 .48 .50 .52 .54 | 


Deptli.^ 
of SM 



12 

1 Foot 

15 

18 
21 

2 Feet* 

27 

30 
33 

36 

3 Feet 

39 

42 

i8^ 
i Feet 'I 


w/ 




















































i^ 






















































1- 




















































:\\ 


\ 


















































i \ 


^V 






















































I- 






^ 


•^ 


ifa/ 










































k 










~~- 


> 


^ 






































K 








■--. 


^ 


^ 


Slob 


le 


































'^'?fe 


h 


i/o,., 












-- 


— 


^ 


F^ 


AJtJ 


li 







Sa 


Its 


















< 


">■► 


+v 


V 


















IC 


Cai 


bon. 


■te~ 


' 


--. 


^^ 







— 


— 


--V 


s 




+**Co-i^ 


ijiO^ 


--~J: 


r> 




















^A 


Ikal 


-Ha 


fdpa 


,n-> 




__. 


:* 









s 


\ 


M 


ev^ 


^ 





























•-' 


■"" 






— ■ 


■^ 




















^aV 


,o&<t 


J^ 


u^ 


■■=^ 


— 






























1- 


> 






/- 


■r^ 


'■^ 










































( 






/ 


y 














































\. 


^' 


y 
















































■ 1 



Fig. II. — Amounts and composition of alkali salts at various depths in black alkali lands covered with 
native vegetation. (Hilgard, Soils.) 

Two types of alkali soils are noticeable : the one is due to the presence 
of carbonate of soda and is called black alkali; the other is due to the 
presence of the sulphates and chlorides of sodium, and is called white 
alkah. The latter is much milder in its effect on plants. In Cahfornia, 
outside the main valleys no important amounts of alkali salts are found 
at depths exceeding four feet. The total amount found in alkali lands 
which show saline efflorescences at the surface in the dry season is from 
one-tenth of one per cent to as much as three per cent of the weight of 
the soil taken to a depth of four feet. Alkali lands also have a high 
lime content and a high potash content — higher than the average 
amount of phosphates; while nitrates are usuaUy scarce or altogether 



lOO FOREST PHYSIOGRAPHY 

absent, though nitrates may occur along the margins of the alkali 
spots. ^ 

In sloping valleys or basins where the central lowest portion receives 
the salts leached out of the soils of the adjacent slopes, occur belts of 
variable width in which the alkali impregnation may reach to a depth 
of ID or 12 feet. Such areas are, however, quite limited and irreclaim- 
able, and the predominating ingredient is usually common salt, as is 
illustrated in the Great Salt Lake basin of Utah, in the Antelope and 
Perris valleys of southern California, and the Yellowstone Valley near 
Billings, Montana.^ The salts of alkali lands are not permanent in their 
vertical position but follow the movement of the moisture, descending 
in the rainy season to the lower limit of the absorbed rainfall, and re- 
ascending in response to surface evaporation, so that at the end of the 
dry season a saline efflorescence may occur or the entire mass may be 
found within a few inches of the surface. 

Carbonate of soda exercises a puddling action on the soil, destroys 
its crumb structure, and renders it almost untillable and impervious. 
It also tends to form a tough impervious hardpan as resistant to roots 
as to implements. Hilgard has shown that the proper treatment of 
alkaline soils is leaching (after treatment with gypsum in the case of 
black alkali), together with subdrainage. Flooding alone is not sufficient, 
for if the process is carried on generally the alkali spots grow larger 
to the destruction of adjacent lands. If cooperative subdrainage is 
carried out the salts may be entirely removed by an excess of irrigation 
water or be carried down to so low a level as to have no injurious efifect 
upon plants. The amount of alkali in the soil may be diminished also 
by cultivating plants that take up considerable amounts of salt, — a 
notable property of the greasewoods (Sarcobatus, Allenrolfea), which 
contain from 12% to 20% of alkaline ash. When grown upon the land 
and then cut and removed, such plants will markedly diminish the 
amount of alkali in the soil. A few such salt-consuming plants are 
fit for pasture, such as the Argentine plant {Atriplex chachiyuyun) and 
the Australian salt bushes {Atriplex halimoides), Vesicaria and Lepto- 
carpus, and a Chilean plant {Modiola procumbens). The results of 
the reclamation experiments of the U. S. Bureau of Soils are surpris- 
ingly good and indicate the range of possibilities in regard to the use of 
alkali lands. ^ Tracts originally covered with a white crust of alkali and 

I E. W. Hilgard, Soils, 1907, pp. 439, 444, 448. 

s Farmers' Bull. U. S. Dept. Agri. No. 88, 1899. 

3 For specific descriptions of the localities where alkali soils have been experimentally 
improved and reclaimed, see C. W. Dorsey, Reclamation of Alkali Soils, 1907, and Reclama- 
tion of Alkali Land in Salt Lake Valley, Utah, Bull. U. S. Bur. Soils No. 43, 1907. 



SOILS OF ARID REGIONS lOl 

supporting a scanty growth of greasewood were sweetened by flooding 
and drainage and then sown to alfalfa, various vegetables, grains, etc., 
with very beneficial results. 

The accumulation of mineral salts at or near the surface has given rise 
to the formation in most arid regions of a characteristic deposit known 
as "caliche." It often consists of a variety of substances, but the most 
common constituent is nitrate of soda. The greatest deposit of this 
sort is found in Chile in the province of Tarapaca, where nitrate of soda 
is produced on a very large scale, practically the whole of the world's 
supply being derived from this desert region. Smaller tracts are found in 
many other deserts, notably in the Southwest as in Death Valley, Cali- 
fornia, but the scale of production in all these cases is decidedly limited. 
In general the layer of caliche is covered with a deposit of earth from a 
few inches to a few feet in thickness. It may consist in part of wind- 
blown material, in part of water-laid material deposited since the caliche 
was formed. The largest beds of caliche are probably due to the crys- 
tallization of mineral salts from bodies of water which have disappeared 
either through a change of climate or a change in the level of the land 
or both. The origin of this class of material is, however, still in doubt, 
and although the result is closely allied to aridity it is not yet clear 
what combination of arid conditions with topography, drainage, and 
chemical character of rock and vegetation brings about its existence. 



CHAPTER VIII 

SOIL CLASSIFICATION 

It has been generally agreed among soil investigators that because 
of the predominating influence of physical characteristics in soil fer- 
tihty, physical and not chemical qualities shall be made the basis of 
soil classification. This decision is strengthened by the immemorial cus- 
tom among agricultural folk of designating soils principally by their phy- 
sical character. The terms sand, gravel, day, etc. (or their equivalents), 
are common non-technical words which convey a fairly definite meaning 
the world over. When, however, a soil is to be scientifically investi- 
gated, its characters strictly defined, and its value and its needs formu- 
lated, somewhat precise terms must be employed, careful experiments 
conducted, and conventional symbols devised which have stricter 
meanings than the colloquialisms of the farmer. Hence a relatively 
refined classification has been elaborated, based primarily upon physical 
character. In examining the accepted classification we should not 
lose sight of the fact that while the forester must acquaint himself with 
it in order to make the literature of soil investigators serve his purpose, 
he generally requires for ordinary field work a somewhat rougher scheme 
of classification. Gravel, sand, silt, clay, and peat or muck are the 
main types he is required to recognize, modifying his choice of terms by 
mention of such secondary qualities as the soil of a particular locality 
exhibits. He will also be required to distinguish between various 
grades of gravel, sand, etc., as coarse, medium, and fine, and it is 
obviously to his advantage to employ for these subdi\dsions the basis 
employed by soil specialists, in so far as this is possible. 

In determining the sizes of soil grains a number of methods may be 
employed; the three principal ones are (a) sieving the soil samples, 
{b) elutriating them, and (c) separating the various grades by the 
subsidence method. 

(a) The sieves used for soil analyses have round holes of carefully 
determined diameter. The unit employed may be fractions of an inch, 
but the smaller units of the metric scale (millimeters) are decidedly pref- 
erable both because of their international acceptance and their easy 
use in computations. The soil samples are sifted after being rubbed 
so as to destroy the lumps or soil crumbs composed of both fine and coarse 



SOIL CLASSIFICATION 



103 



material that behave in some respects as large individual particles the 
size of the lumps. Separation may be more easily accomplished by 
playing water on the sieve; without it the clay particles and even the 
silt particles tend to cling to the sand as soon as the grain sizes in the 
latter fall much below I2 mm. 

{h) The elutriator, Fig. 12, is an instrument employed to separate 
soil grains of different sizes 
(after removal of the clay 
by subsidence) by an as- 
cending current of water 
at various fixed velocities. 
The soil grains are carried 
off in exact conformity to 
their several sizes or volume 
weights. The maintenance 
of the current at a fixed 
velocity for a long enough 
period will result in the 
practically complete re- 
moval of all grains below a 
certain size. The different 
velocities are adapted to 
certain desired grain sizes, 
and the volumetric determinations that follow elutriation form the basis 
for classification. 

(c) The subsidence method is based upon the assumption that if a 
soil sample is thoroughly mixed in water the different grain sizes will 
settle according to their weights. A successful outcome requires the 
removal of the clay by repeated sedimentations of the non-clay material, 
the decantation of the water in which the suspended clay particles are 
held, and the final sedimentation of the coarser grades. The necessity 
for the removal of the clay is due to the greater viscosity of the water 
in which the clay is suspended and its interference with normal and 
accurate sedimentation. The clay itself is determined from the several 
clay waters by evaporation of the water. Precipitation will not suffice, for 
the finest colloidal clay will not subside for years, — a condition thought 
to be due to a change in its physical and possibly in its chemical nature.^ 
A defect of the subsidence method is the impossibility of abstracting all 
the clay, a defect the more serious because of the high importance of the 

1 W. H. Brewer, On the Suspension and Sedimentation of Clays, Am. Jour. Sci., vol. 2g, 
1885, p. I. 




Fig. 12. — Elutriator (Hilgard's) in position for soil analysis. 



I04 FOREST PHYSIOGRAPHY 

clay constituent of soils (p. 35). Some clay particles are invariably 
carried down by heavier constituents and deposited with them. A similar 
result does not occur in elutriation because of (i) the agitation (which 
prevents flocculation into heavy aggregates) of the ascending current 
and (2) the grain sizes are expelled in reverse order, the finest first, and 
so on. 

Purpose of a Soil Analysis 

The physical analysis of a soil is not alone for the purpose of finding 
a name for it in the series proposed in the table, Appendix A. This is 
the least of its purposes. It aims, in addition, clearly to present the 
controlling constituent among the soil grains. Soils are not generally 
composed of grains rather equally distributed among the several sizes. 
Some particular size usually predominates, and gives the soil its strongest 
individual character. This is clearly illustrated by the Volusia soils 
spread over some 10,000,000 acres of western Pennsylvania, southern 
New York, Ohio, and West Virginia. They are poor in their present 
condition, yet nothing in their chemical nature suggests poverty. Their 
unproductiveness is due largely to improper drainage, for their physical 
composition is such that the natural drainage is not adequate; acid 
therefore forms and accumulates and makes the soil sour. Their im- 
provement is not to be sought in the use of fertilizers alone, for the 
fine-grained fertilizers by themselves would still further clog the soil 
pores. It is suggested that adequate drainage and deep aeration would 
prove remedial.^ 

The remedies proposed are particularly interesting because they are 
among the relatively small number which the forester finds it possible 
to apply to economic advantage over large areas. The forester can not 
fertilize the ground by the application of manures or mineral fertilizers; 
the very scale of his work makes it impossible to do more than enable a 
forest soil to improve itself by encouraging processes already in action. 
This he is able to do in many ways. Proper cutting and seeding or 
replanting are almost always possible in both the physical and the 
commercial sense of the term, and by maintaining shade the drying of 
the surface soil, in which seedlings make their first growth, is prevented. 
Proper drainage is also feasible and is at once a means of partly control- 
ling the kind of growth and the rate of growth. 

It is fundamental in drainage to ascertain the nature of the subsoil 
as well as the soil. If the subsoil is open and porous it is likely to be 
dry; if clay forms the subsoil it will probably be wet and by capillarity 

1 M. E. Carr, The Volusia Soils, Bull. U. S. Bur. of Soils No. 60, igog, pp. 21-22. 



SOIL CLASSIFICATION 105 

supply the surface soil with water in the dry season. Not only for this 
reason, but also because so important a part of the root systems of trees 
occurs in the subsoil, is it necessary to secure data as to its nature and its 
effects upon the surface soil in different seasons. 

Different Bases of Soil Classifications 

It is unfortunate that no general scheme of classification has been 
universally adopted by soil physicists. In Appendix A the scheme 
of the U. S. Bureau of Soils is described because the literature of this 
Bureau is now both extensive and valuable and reference to it indis- 
pensable on the part of any one beginning the study of the soils of a 
given region. Nevertheless it should be noted that many other bases 
of subdivision of soil types are in vogue. It has been proposed by 
Hilgard and others, that all constituents of soils that are too large to 
pass through a sieve with meshes 0.5 millimeter in width should be 
called the "soil skeleton" and that the remaining constituents that pass 
through the sieve should be called "fine earth." He regards the fine 
earth as having a special relation to plant life as food material and 
through its physical attributes. For the purposes of ecologic studies 
Warming distinguishes six different kinds of soil as follows ^: 

Rock soil. Clay soil. 

Sand soil. Humus soil. 

Lime soil. Saline soil. 

Soils may be distinguished also by classes, as rigid, stiff, mellow, lax, 
loose, and shifting, in order to express various grades of compactness. 
Hilgard suggests the use of broad types such as sand, clay, and humus. 
Considered in reference to their origin, soils may be classified as 
sedentary and transported. A sedentary soil may then be either 
residual where it remains upon the rock from which it was derived or 
colluvial where it is subject to slow down-hill movement on hill slopes. 
Transported soils may also be divided into alluvial where the soil is 
deposited on bench lands or flood plains, and eolian where it is de- 
posited by the wind. The most common classification is based on tex- 
ture, as gravel, sand, silt, clay, and their subdivisions and derivatives. 
Again, soils may be called humid or arid according as they are formed 
in one or the other of these climates. Or a soil may be classified 
according to its chemical properties. Thus, we have a lime soil with 
its lime-loving vegetation, or a magnesium soil, or a soil exceptionally 

1 oncology of Plants, Ox. ed., 1909, p. 60. 



I06 FOREST PHYSIOGRAPHY 

rich in potash or gypsum. A classification based on the distribution 
of vegetation is often helpful but the soil requirements of plants are 
not rigid except in the case of extreme types of soils and plants. 
Doubtless the physical classification has the widest practical impor- 
tance since physical features most commonly have a fundamental 
control over vegetation and are the most unchangeable. The ideal 
classification would be adaptable to, and would take cognizance of, all 
important soil characters. It is at least certain that no single scheme 
is applicable to all kinds of soils in all kinds of climates .'^ 

With this brief suggestion of the nature of other classifications in mind 
the student is referred to Appendix A for a description of a suggested 
outline of a soil survey with such description of the field methods re- 
quired as bear on soil studies practicable in forestry. 

1 Hilgard and Loughridge, The Classification of Soils, Verh. der II Int. Agrogeologen- 
conferenz, Stockholm, igii. 



PART TWO 
PHYSIOGRAPHY OF THE UNITED STATES 



CHAPTER IX 

PHYSIOGRAPHIC REGIONS, CLIMATIC REGIONS, FOREST REGIONS 

Introduction 

Physiography is indispensable to the environmental study of or- 
ganisms of every kind, whether trees, or men, or bacteria. Soil, topog- 
raphy, and climate are positive forces in the development of forests 
and the harvesting of forest products. They underline the main possi- 
bilities as well as the main lim.itations of nature. We have already seen 
that soil in at least small amounts is a necessary condition of tree 
growth; of the same order of importance are the facts that the broader 
forest distributions depend upon climate, while the accessibility of for- 
ests depends to a large extent upon topography. It is doubtful, for 
example, whether some of the best timber of the Sierra Nevada will 
ever be harvested because of topographic difficulties — steep canyon 
walls, sharp spurs, and remoteness from transportation lines. Climatic 
. conditions exclude trees from the larger part of the arid and semi-arid 
West and from the higher, colder, and windier parts of the western 
mountains. Forests are excluded also from great areas of bare rock 
outcrop in regions of glacial denudation or from soils rendered infertile 
by extreme physical or chemical properties. The forester must take 
account not only of these relations but also of the larger relations of 
forests to stream flow and soil erosion. Each soil type has its own 
peculiar water-holding or water-shedding capacity, each topographic 
province has certain slopes upon which either agriculture or forestry 
can or can not be conducted, each natural region has its own climatic 
possibilities and restrictions, a study of which enables the forester to 
improve natural conditions and repress harmful forces to the benefit of 
mankind. 

It is our purpose in these pages to present the physical basis of 
forestry in the United States. No attempt is made, however, to discuss 

107 



lo8 FOREST PHYSIOGRAPHY 

either regional ecology or the principles of ecology. The ecology of the 
forest is regarded as a subject which possesses a body of facts and laws 
of its own. The single object of this book is to acquaint the forester 
with the geographic basis of his work, with such references to the forest 
as point the direction of his more special subjects. 

This attitude should be appreciated here, lest the organization of the 
following chapters be misunderstood. For example, a forester requires 
a certain group of physical data in developing, let us say, the forests of 
the Black Hills. It is our object to discuss not the silvicultural or 
lumbering methods best adapted to the Black Hills and the relations 
of these to the physical geography of the region, but to make the student 
so familiar with the geography that a knowledge of it may be assumed 
when he begins a study of the forestry. 

Physiographic Regions 

The description and explanation of any large and varied portion of 
the lands proceed naturally by subdivisions, each subdivision embracing 
a tract in which the topographic expression is in the main uniform. 
Since uniformity of topographic expression is achieved only when geo- 
logic structure, physiographic process, and stage of development in the 
geographic cycle are also uniform, each subdivision has an essential 
uniformity or unity of geologic and physiographic conditions. It is 
customary to speak of each subdivision as a natural region or province, 
and to bound each region by lines which represent the limits of unity. 
In some cases the boundary lines are very precisely located, as along 
the eastern edge of the Allegheny Plateau in Pennsylvania, or the 
western edge of the Colorado Plateaus in Arizona, where great scarps 
mark out sharply defined borders; in other cases the transition zone 
between provinces is relatively wide and has characteristics which par- 
take of the nature of both adjoining provinces, as between the Columbia 
Plateau of southern Oregon and the Great Basin south of it. 

It must not be supposed that the idea of physiographic unity is 
applied in an absolutely rigid manner. Some of the physiographic 
provinces appear to have great topographic variation and but little 
unity. In such cases it appears at first sight impossible to group the 
forms in a rational manner until soil, climate, topography, and geologic 
structure are all examined, when prevailing or group characters always 
become apparent. Exceptions to group qualities are often observed, 
and in some cases these are of great importance, but on the whole they 
affect only the minor physiographic features. Thus the northern Rockies 
of Montana and Idaho are in striking contrast to the high plains on either 



PHYSIOGRAPHIC, CLIMATIC, AND FOREST REGIONS 109 

side, — the Columbia lava plain of Washington on the west and the Great 
Plains of Montana on the east. This contrast between a belt of high, 
rugged mountains and gently rolling, bordering plains forms a primary 
basis for subdivision. Nevertheless the traveler in crossing the northern 
Rockies finds the landscape changing continually. Everywhere the 
ranges trend in the same general direction, but the kind of rock, the 
structure and hardness of the rock, and the kinds of dissection affecting 
the range masses vary from point to point; everywhere the major 
valleys have a distinctive trough-like cross section, but the minor valleys 
are of many varieties. No two ranges, therefore, are alike in detail, 
but all are alike in being rugged and high, while the bordering lands 
are smooth and low (relatively). Some of the mountains are dissected 
plateaus, as the Clearwater Mountains of Idaho; others are dissected 
anticlines and synclines, as the Lewis and Livingston Mountains of 
Montana ; yet they are all alike in being deeply dissected. 

The broad similarities among the features of a physiographic province 
are frequently expressed in the name of the province, as "Prairie Plains,''' 
or "Colorado Plateaus," or "Great Basin"; yet the Prairie Plains are 
locally rough, as where high and irregular morainic belts cross them, 
the Colorado Plateaus are diversified by volcanic mountains like Mt. 
Taylor and San Francisco Mountains, whose summits reach above 
timber line, and the Great Basin consists of many independent basins 
broken by, and mutually separated by, mountains of marked height 
and ruggedness. The dissimilarities among the features of a region 
may be classified and grouped by subregions. The Older Appalachians 
(Chap. XXVIII) for example have certain very distinctive and uniform 
features over a great belt of country from Maine to Alabama, such as 
their great geologic age, their highly complex structure, their prevailingly 
crystalline character, and the tremendous erosion which they have suf- 
fered. But throughout the region marked dissimilarities also occur which 
require recognition. The scenery about Asheville, North Carolina, is 
quite unlike that about New Haven ; the mountain basin in the first case 
falls in the Appalachian Mountains, a subdivision of the Older Appalach- 
ians, the valley lowland of the second case lies in the glaciated New 
England subdivision of the same province. 

Many of the physiographic regions of the United States are of 
great size. The Great Plains are as extensive as European Russia; the 
Lower Alluvial Valley of the Mississippi is at least half as large as 
Italy; the Alps are less extensive than that part of the Rockies south 
of the international boundary. Many individual topographic features 
are developed on a large scale. Hurricane Ledge, an eroded fault 



no FOREST PHYSIOGRAPHY 

scarp in the Colorado Plateaus, is 700 miles long, the Great Valley 
of the Newer Appalachian region extends with but local interruptions 
from Alabama to Quebec, the Grand Hogback of western Colorado 
is a bold escarpment of erosion which extends unbroken for over 200 
miles. 

In addition to the great size of individual provinces and features is 
the great variety of physiographic features which the country exhibits. 
The physiography is also in many respects unique. Exploration has not 
revealed anywhere else on the earth structures and forms like those 
of the Colorado Plateaus, either in respect of scale or perfection of de- 
velopment. The Newer Appalachian ridges and Valleys are so perfectly 
developed that "Appalachian structure and topography" has become a 
technical phrase. The till sheets of the upper basin of the Mississippi, 
in the heart of the continent, are so extensive and their succession so 
complete that the history of the glacial period was first worked out to 
partial completeness in America. The Columbia lava flows constitute 
one of the few really great basalt fields of the world. 

We should ascribe to the great variety of physical conditions in the 
United States no small share of the general interest in American forestry, 
for the forests and forest problems are almost as varied as the relief 
upon which, either directly or indirectly, they so commonly depend. 
The vital relation of the forests of the arid West to the general welfare 
of the people has given western forestry a scientific interest not exceeded 
elsewhere. Man's control of the desert had its beginning in his control 
of water. At first that control was in the nature of art; now it is in the 
nature of science. As much care was at first bestowed upon the ritual 
of rain as upon the construction of a dam; we now study the laws of 
rainfall, measure its several dispositions, exercise control over it in measur- 
able degree, relate cause and effect, and know the limits of irrigation 
enterprises before they are begun. Throughout the West the problem 
of water control has been found to be also a problem in forest control 
and grass control. Irrigation, forestry, and grazing are parts of one 
scientific problem. Of lesser but still of great importance are the rela- 
tions of run-off and forests in the humid East, where over large areas a 
mountainous relief diminishes the value of the land for agriculture and 
increases its value in relation to forests and stream flow. Mountain 
influences are extended out upon the plains, where resides a dense agri- 
cultural population whose commerce and towns and fertile valley lands 
are often largely dependent upon the behavior of the mountain-born 
streams. 



PHYSIOGRAPHIC, CLIMATIC, AND FOREST REGIONS 



III 



Climatic Regions 

The determining factors of climate are chiefly latitude, the relative 
distribution of land and water, the elevation of the land above the sea, 
and the prevailing winds; the most important climatic eleynents are' 
temperature, moisture, wind, pressure, and evaporation. The climatic 
elements are shown graphically on the accompanying series of maps for 
North America. Among them temperature and rainfall are of most 
importance in relation to forests, and a brief discussion of these elements 
of our climate is therefore presented in this chapter. In Plate I, rep- 
resenting the climatic provinces which correspond with the life regions 
of Merriam,'^ they are combined in such a way as to show their effect 
upon the life of the continent. 




Fig. 13. — Koppen's classification of climates in relation to vegetation. Tracts enclosed by broken line 
have distinct dry seasons (rain probability < 0.20). Ai, Liana; A2, Baobab; Bi, Garva; B2, Simoon; 
B3, Mesquite; Bt, Prairie; C2, Hickory; Cs, Corn; C4, Olive; Cs, Heath; C7, High Savanna; Di, Oak; 
D2, Birch; Ei, Arctic Fox. (Ward, Climate.) 



TEMPERATURE 



The temperature map, after Koppen, Fig. 14, is peculiarly useful to 
a forester, since on it temperatures are not reduced to sea level and the 

' C. H. Merriam, Life Zones and Crop Zones of the United States, Bull. Div. Biol., U. S. 
Dept. Agri., No. lo, 1898. The fourth edition of this map forms the basis for Plate I. 



112 



FOREST PHYSIOGRAPHY 



boundaries of the various belts have certain definite relations to tree 
growth. 

"A normal duration of a temperature of 50^ for less than a month fixes very well the polar 
limit of trees and the limits of agriculture. Near this line are found the last groups of trees in 
the tundras. A temperature of 50° for four months marks the limit of the oak, and also closely 
coincides with the limits of wheat cultivation." ^ 

The greater part of the United States lies in the belt of westerly winds, 
hence we should expect marine temperature influences to be felt farther 
inland on the Pacific or windward coast than on the Atlantic or leeward 
coast. However, the Pacific coastal tract has a relief including high 
mountain ranges trending at right angles to the prevailing winds, hence 
marine influences affect a belt of country sharply limited on the east. 
They do not extend farther inland than the Sierra Nevada in California 
and the Cascades in Oregon and Washington, except along the valley 
of the Columbia (which cuts across the Pacific mountains), where un- 
usually high temperatures prevail for some distance east of the Cascades. 
Washington, Oregon, and California have strikingly equable temper- 
ature conditions. On the Atlantic coast marine influences do not extend 
so far inland as a rule nor are they so pronounced. They are, however, 
distinct, as is shown both by the lower absolute and mean monthly tem- 
peratures at a shore station like New London as compared with a sta- 
tion hke Middletown, Connecticut, 20 miles inland. Southern species of 
birds and plants follow the Atlantic coast in narrowing belts surprisingly 
far toward the north. The northernmost occurrence of persimmon trees, 
a southern species, is at Lighthouse Point, Nev/ Haven. The temper- 
ature contrasts between the two coasts are shown in the following table. 

CONTRASTS BETWEEN ATLANTIC AND PACIFIC COAST TEMPERATURES^ 



Stations , 


Latitude 


Annual 
Mean 


Winter 
Mean 


Summer 
Mean 


Savannah, Ga 

San Diego, Cal 

Cape May, N. J 

San Francisco, Cal.. 

Nantucket, Mass 

Eureka, Cal 

Chatham, N. B 


32° 5' 
32 43 

38 50 
37 18 

41 17 
40 48 

47 3 
46 17 


66° F. 
61 

54 
56 

49 
52 

39 
50 


52° F. 
55 

36 
'' 

33 

47 

13 

42 


8i°F. 
68 

72 
59 

6S 
56 

63 
58 


Fort Canby, Wash 



1 R. DeC. Ward, CHmate, 1908, p. 28. 

2 A. J. Henry, Climatology of the United States, Bull. Q, U. S. Weather Bureau, 1906, 
p. 26. The statistical data in the section on climate have been derived chiefly from this source. 



PHYSIOGRAPHIC, CLIMATIC, AND FOREST REGIONS 



113 




Fig. 14. — Temperature zones of the western hemisphere. (Ward, adapted from Koppen.) 



114 



FOREST PHYSIOGRAPHY 



It will be noted from the table that the winter means on the Atlantic 
coast are regularly lower than those on the Pacific, since, being on the 
leeward side of the continent, continental influences are more strongly 
marked than marine. The summer means are all higher for the same 
reason : the land is always warmer in summer and colder in winter than 
the sea. 

The greatest extremes of temperature are experienced in. the interior 
of the country far from the influence of the oceans, where the continental 
type of climate prevails. The valleys of eastern Montana experience 




Fig. 15. — Normal surface temperatures for July. 



the lowest absolute temperatures; —65° below zero was recorded at 
Miles City, Mont., January, 1888. The whole plains region in the latitude 
of the international boundary is subject to great and sudden variations 
of temperature, since its open and vast expanses are exposed both to 
the cold winds from the mountains and the north, and to hot winds 
from the south. The 100° maximum at times extends into the Cana- 
dian Northwest. The northerly winds are sometimes of great velocity 
and in winter are often attended by light, dry snow, conditions which 
reach their culmination during a blizzard, when the wind may attain 
a velocity of 60 miles an hour. High winds in summer are often 
attended by dust and give rise to the "dust storms" of the plains. 



PHYSIOGRAPHIC, CLIMATIC, AND FOREST REGIONS 



115 



When they are marked by high temperatures they may be even more 
harmful to crops than the winter bHzzards are to Hvestock. 

Maximum temperatures of 100° and over are experienced in all parts 
of the United States except in the higher portions of the Atlantic and 
Pacific Cordilleras, the immediate coasts of both oceans north of 40°, 
in the peninsula of Florida, along the Gulf coast, and in portions of the 
Great Lake region. The highest recorded temperature in the entire 
country is 130°, recorded in the Colorado Desert in southern California. 
Maximum temperatures of 112° to 115° are frequent in southwestern 
Arizona and southern California. The only Weather Bureau stations 




Fig. 16. — ^ Normal surface temperatures for January. 



in the United States where a minimum temperature below freezing 
has not been experienced are Key West, Fla., and San Diego, Cal., 
with absolute minima of 41° and 32° respectively. South of the mouth 
of Chesapeake Bay the Atlantic coast has never experienced a temper- 
ature below zero, nor have zero temperatures ever been recorded along 
the Gulf coast, at any point on the Pacific coast, or in the Great Valley 
of California. The mountain summits of both the Atlantic and the 
Pacific Cordilleras have minima comparable to those experienced on the 
north-central Great Plains and in the Arctic regions. The lowest 
recorded temperature on Mount Washington, N. H.. (6293 feet), is 
— 50°, the lowest on Pikes Peak, Col. (14,134 feet), is — 37°. 



ii6 



FOREST PHYSIOGRAPHY 




Fig. 17. — Average date of list killiag frost in Autumn. 




Fig. 18. — Average date of first killing frost in Spring. 



PHYSIOGRAPHIC, CLIMATIC, AND FOREST REGIONS I17 

The mean annual range of temperature is about 30° in the states of 
the Gulf and Atlantic Coastal Plain, 40° to 50° in the interior valleys, 
Rocky Mountain region, and Middle Atlantic States, and from 55° to 
65° over the northeastern Rocky Mountain slope and eastward to Lake 
Superior. The greatest daily range occurs in the arid and semi-arid 
Southwest on account of the prevailingly clear skies and the lack of 
vegetation; the greatest mean daily range (30° to 35°) is in the Plateau 
region, the least (8° to 12°) is along the Pacific and Gulf coasts. East 
of the Mississippi Valley the mean daily range is generally less than 20°. 

PRECIPITATION 

The chief causes of an abundant rainfall are (i) nearness to the 
ocean or other large body of water such as the Gulf of Mexico or the 
Great Lakes in the United States, (2) location within or near the track 
of cyclonic storms, and (3) mountain ranges athwart the rain-bearing 
winds. The western slopes of the Coast Ranges of Oregon face the 
ocean and run at right angles to the westerly winds, and their rainfall 
exceeds 100 inches a year; the Ohio Valley lies in the track of the more 
or less regular cyclonic storms that move northwestward from the Gulf, 
and receives a rainfall of 40 to 50 inches a year; nearness to the sea 
gives the greater part of the Atlantic and Gulf coasts a higher rainfall, 
50 to 60 inches, than is enjoyed by any portion of the eastern half 
of the country except the mountains of western North Carolina. By 
contrast the mountain-rimmed parks of Colorado, and the Great Basin 
of Nevada, are regions of diminished rainfall; the coast of southern 
California owes its dryness chiefly to its position outside the belt of 
cyclonic storms; the dryness of North Dakota is chargeable chiefly to 
remoteness from the sea, although in this, as in the other cases cited, 
the rain-producing or rain-resisting forces commonly operate in com- 
bination with other forces, so that the influence cited should be under- 
stood to be the predominating and not the sole influence. 

Rainfall is always due to the cooling of the air to and below the point of saturation. This 
may be accomplished (i) by the rise of air on a mountain flank — the air expands on rising 
and since the heat of the air supplies the energy for expansion, the air is cooled to and beyond 
the point of saturation and rain falls; (2) by convectional air currents produced by a local 
overturning of the lower air as during a summer thunder shower; and (3) by radial inflow and 
ascensional movement, as in cyclonic storms, with expansion and cooling to the point where 
rain falls. 

The seaward slopes of the Coast Ranges of Oregon and Washington 
receive the heaviest rainfall in the United States, from 60 to 150 inches 
a year. Rains are frequent during the entire year, but most frequent 



ii8 



FOREST PHYSIOGRAPHY 



during the winter season, from November to May. The rain-bearing 
winds change from southeasterly to westerly with the approach and 
passage of cyclonic storms. The rain begins with the southeast wind 
and ends with the westerly wind. The result is that the leeward or 
eastern slopes of the mountains are also well watered, though the fall is 
lighter than that on the windward or western slopes. Northerly winds 
bring fair weather at all seasons. Southward from the well-watered 
strip along the northern part of the Pacific coast the rainfall decreases 
rapidly, falling from 67 to 22 inches between the northern boundary of 



Vio" lfc.\ VJ-I n? lli^ 109' 105° 101' 97' 9'3° 89' 83" 61 




Fig. 19.— Mean annual precipitation in the United States reduced to inches of rainfall. 
Adirondacks, White Mountains, and Black Hills islands. (U. S. Geol. Surv.) 



Note the 



California and San Francisco. Toward the south it continues to de- 
crease and falls to a minimum of less than lo inches at San Diego, in the 
horse latitude belt of light uncertain winds between the westerlies and 
the trades. The Pacific coast thus exhibits a range in rainfall of about 
100 inches. 

The main Pacific coast valleys, embracing the Great Valley of Cali- 
fornia, Salton Sink, the Willamette Valley, and the Puget Sound depres- 
sion, have a much lighter rainfall than the rain-obstructing Coast Ranges, 
since they lie in the lee of the latter. The valley of southern Cahfornia 
is an extremely dry desert. In the Great Valley the rainfall varies from 
about 10 inches at Fresno in the south to 25 inches in the north; the 



PHYSIOGRAPHIC, CLIMATIC, AND FOREST REGIONS II9 



.IW 125- .,„< I2i 



H.T 6r 




Fig. 20. — Absolute minimum temperatures. 



■ 129- pl2S' 7 .S >'^-r. 1 17- in- 109' 105' 101° S7 



Wl° -31' 77' 7:r M' 




Fig. 21. — The average annual humidity of the air in the United States. 



I20 



FOREST PHYSIOGRAPHY 



rainfall of the Willamette Valley varies from 25 inches in the south 
to 45 inches in the north; while the Puget Sound region has an average 
rainfall of about 45 inches. The precipitation increases rapidly east- 
ward as the winds ascend the western slopes of the Sierra Nevada and 
the Cascades. It reaches a maximum of about 100 inches in Wash- 
ington and Oregon, and from 40 to 80 inches in California at elevations 
between 3500 and 5000 feet. Beyond this point the precipitation 



125° 121° 117° 113° 109' 1H5' 101° 97° 93' 




Fig. 22. — Percentage of annual rainfall received in the six warmer months, April to 
September inclusive. 



diminishes again toward the summit and becomes insignificant at the 
eastern base of the mountains. 

The great height and continuity of the Sierra Nevada and the Cascades 
cause these mountains thoroughly to obstruct the westerly winds in 
respect of moisture, with the result that great stretches of country east 
of them are arid wastes. Where ranges of exceptional height occur in 
the country east of the Cascades and the Sierra Nevada the rainfall may 
exceed 25 inches a year, but by far the greater part of the region has 
less than 12 inches a year. Southwestern Arizona and southern Cali- 
fornia are the driest regions in the United States, and the rainfall of the 
lowlands is almost wholly confined to the winter months. In the rain 
shadow of the Sierra Nevada the mean annual rainfall is between 5 and 
6 inches and locally as low as 3 inches. It is characteristic of the region 



PHYSIOGRAPHIC, CLIMATIC, AND FOREST REGIONS 121 

that occasionally some portion of it receives a rather abundant rainfall. 
About once in six years the greater part of the rainfall of a locality 
conies in a single month. In 1891, for example, 2.5 inches or 93% of 
the annual rainfall of the lower Colorado Basin fell in January. In 
January, February, and March, 1905, 8 inches of rain fell at Yuma, 
Arizona, whereas the average annual rainfall of that place is but 2.7 
inches. 

The Rocky Mountain region rises to such a height as to provoke a 
heavier rainfall than the plateaus and basins on the west, though the 
remoteness of the region from the sea gives it a much lighter rainfall than 
occurs in the southern Appalachians of far lower elevation, or the 
relatively low Coast Ranges of Oregon. During the winter the western 
windward slopes of the Rockies are more heavily watered than the east- 
ern, but the reverse is true for portions of the system during the spring 
and summer. In New Mexico and western Texas the mountains of the 
Trans-Pecos region have a greater rainfall than the surrounding plains 
and basins, but it is never heavy in an absolute sense. It comes in July 
and August and appears to be rather evenly distributed on all sides as if 
due to local updraft of air from plains to mountains. Nowhere does 
more than 50 inches of rain occur in the Rockies and the average 
amount is far smaller. The rainfall is very unevenly distributed, as 
might be expected owing to the irregular trends of the intermont basins 
and mountain ranges and the variable dispositions and heights of the 
mountains. The maximum precipitation occurs probably in northern 
Idaho; the minimum is between 6 and 8 inches and falls in San Luis 
Park in south-central Colorado. 

Eastward of the Rockies as far as the Atlantic coast the topographic 
features lack great height, hence the rainfall distribution is controlled 
chiefly by the frequency and direction of movement of the rain-bearing 
cyclonic storms. The greater height of the Unakas, Great Smokies, and 
associated ranges in western North Carolina and South Carolina and 
northern Georgia cause their rainfall to exceed that of any other region 
east of the Pacific mountains. It is more than 70 inches a year. The 
rugged and high eastern portion of West Virginia, the Adirondacks, and 
the White and the Green mountains are other centers of heavy rainfall 
that owe their influence upon climate to their greater height. A heavier 
rainfall depending not on elevation but on nearness to the sea and 
to position within the track of frequent cyclones occurs in southern 
Louisiana and Alabama, — 60 to 70 inches. 

The Great Plains region has a diminished rainfall owing to its position 
in the rain shadow of the Rockies and its remoteness from the sea. 



122 FOREST PHYSIOGRAPHY 

Fortunately such rain as falls comes chiefly in the summer or growing 
season. From the loist meridian to the Rockies the rainfall is from 
lo to 15 inches. Eastern Colorado is a region of small precipitation, with 
an average fall of about 12 inches and a maximum yearly fall rarely 
in excess of 20 inches. In western Kansas the precipitation of the 
driest year was 9.9 inches; of the wettest, 33.7 inches. The last-named 
illustration is typical of the wide differences between the extremes of 
rainfall in the arid and semi-arid portions of the West. The wettest 
years have a rainfall suflEiciently great for agriculture; the means and 
minima are far below the necessary amount. 

Of the seven climatic and life provinces of North America, Plate I, but 
four fall within the limits of the United States, except that the southern- 
most or tropical province touches southern Florida and the lower valley 
of the Colorado, and the northernmost or Arctic province is developed 
on a few of the highest summits like Shasta in northern California and 
Bkckfoot Mountain, Montana. 

The Boreal province is developed in the southern Appalachians of 
western North Carolina, eastern West Virginia, the Catskills, the Adi- 
rondacks, the White ancl the Green Mountains, and in the Superior 
Highlands of northern Michigan and Wisconsin and on all the main 
divisions of the Pacific Cordillera, where its upper limit coincides with 
the timber line. It is marked by a low mean annual temperature, 
generally between 32° and 40°, by long, cold winters, and in general by 
a heavy snowfall. Its forest growth is spruce and pine in New England, 
spruce and balsam in North Carolina, chiefly white pine in Michigan 
and Wisconsin, and spruce, fir, and cedar in the Pacific Cordillera. 

The greater part of the mountain forests of the United States is 
found in the Transition province which includes the cool temperate 
portions of the country with a generally high mean annual precipitation. 
The mean annual temperature is about 45°, but the temperature is in 
general marked by frequent and sudden changes. Snow falls through- 
out the entire province, though it is variable in amount owing to differ- 
ences of elevation, exposure, etc. 

In the northern portion of this province both broad-leaved deciduous 
trees and conifers grow; similarly in the west, scattered growths of oak, 
pinon pine, and sycamore of the lower mountain slopes mingle or shade 
into the spruce and yellow and white pines of the upper slopes. The 
province as a whole has few distinctive plants; it is marked rather by 
the mingling of southern species that here find their northern (on the 
mountains their upper) limit and of northern species which find their 
southern (or lower) limit of occurrence. 



PLATE I 




Scale of Miles 
160 15 S'O 25 '• li5o 200 sSo 

Plate I. — Climatic and Life Provinces of North America. 



PHYSIOGRAPHIC, CLIMATIC, AND FOREST REGIONS 1 23 

1 

The western division of the Upper Austral province is so dry that 
agriculture without irrigation is impossible and tree growth is limited to 
the heads of the better watered alluvial fans and the banks of streams.. 
The eastern portion of the province was originally covered with a varied 
and dense forest of hickory, maple, oak, and chestnut, as in the Ohio 
Valley and the Piedmont and the Appalachian Plateaus. The climate 
is warm temperate, with a long summer season. 

The Lower Austral province resembles the Upper in the western part 
of the country in its general treelessness except along the streams. 
East of the looth meridian the climate is wetter, and throughout the 
entire Gulf and Atlantic Coastal Plain the temperature and rainfall are 
favorable to the growth of great forests of southern species of pine and 
of cypress. The winters are very mild, snowfall is absent, and the long, 
hot summers have an abundant rainfall. The mean winter tempera- 
ture is 40° to 52°, the summer temperature from 75° to 80°. 

FOREST REGIONS 

A single unbroken forest belt extends across North America, the 
spruce forest of Canada. Its northern border, a timber line determined 
by cold and physiological dryness, extends from Hudson Bay north- 
westward to the head of the Mackenzie delta, thence westward and 
southwestward across Alaska. Its southern margin is the 60th parallel 
in the Canadian Northwest and the 50th parallel in the Great Lake 
region. Black and white spruces, poplar, canoe birch, aspen, and tama- 
rack are typical growths; the presence of only a few species of trees is 
characteristic. The spruce forest includes a large part of the lake region 
of North America with an abundance of lakes and swamps (p. 565). 
The spruces and the gray pine grow on the uplands between lakes and 
swamps; poplar, dwarf birch, willow, and alder occupy the cold wet bot- 
tom lands. While the trees attain fair size on the southern portions of 
the belt in which they occur, they are never large, and decrease notably 
in size toward the north, where they finally become so stunted as to be 
of little economic importance. 

Southward from the broad transcontinental forest belt are an Atlan- 
tic forest, a Pacific forest, and a Rocky Mountain forest. The two 
intervening belts of country — the Great Plains and the Great Basin 
— are forestless though not treeless. This distribution is controlled 
largely by rainfall, though the distribution of species within each region 
is also controlled by insolation, temperature, wind velocity, water supply, 
and geographic relation to postglacial centers ' of dispersal. By the 
same token the forests are not distributed evenly over a given region, 



124 



FOREST PHYSIOGRAPHY 




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'IS ° 



PHYSIOGRAPHIC, CLIMATIC, AND FOREST REGIONS 125 

but vary from windward to leeward slopes, from warm southern to cool 
northern slopes, and from dry to wet situations as controlled by more 
local conditions. 

The eastern or Atlantic forest tract consists largely of hardwoods, 
though large tracts of conifers are also found; the western forests are 
principally conifers of unrivaled size and beauty and hardwoods are 
comparatively rare. The great variety and in some cases the great size 
of the trees of the Atlantic forest are distinctive features. The primary 
divisions of the Atlantic forest belt are (i) a belt of conifers, (2) a white 
pine belt, and (3) a belt of southern pines. 

The belt of conifers in which the white pine is the most important 
species extends from southeastern Canada and Massachusetts west- 
ward to northern Michigan, Wisconsin, and Minnesota. It reaches its 
best development in the light, dry, sandy soil of the glacial drift in the 
northern part of the southern peninsula of Michigan. White cedar, 
hemlock, fir, larch, and spruce are other conifers of minor importance in 
the tract. 

South of the white pine belt is a belt of hardwoods which extends 
through the Great Lake states and the larger part of the great Appa- 
lachian region. The most notable types of trees are many species of oaks, 
several kinds of hickory, the chestnut, basswood, magnolia, tulip tree, 
and Cottonwood. In this belt the hickories reach their greatest size 
in the Ozark region, the oaks in the central and southern portions of the 
eastern United States, the tulip tree in Kentucky. Among the excep- 
tions to the characteristic growths of this division may be mentioned 
the spruce and hemlock forests on the summits of the Pisgah and other 
ranges in western North Carolina, where boreal conditions prevail. 

The Atlantic and Gulf Coastal Plain is occupied by longleaf, short- 
leaf, loblolly, and slash pines. The first two occupy dry sandy uplands 
for the most part; the loblolly pine grows best on the drier portions of 
the moist lowlands of eastern Texas. 

Among the trees of the Pacific coast forests in the United States the 
red or Douglas fir is the most important. It has its best development in 
the wet Puget Sound region, where it grows to a height of several hundred 
feet. It is associated with the tide-land spruce, hemlock, and red cedar. 
This portion of the Pacific forest is one of the densest and commercially 
one of the most valuable in the country. Southward and eastward the 
forest changes in character. In northern CaHfornia, where the rainfall 
is heavy, the redwood is the most important forest tree, and between 
it and the fir forest on the north is a tract occupied by the Port Orford 
cedar. The dry and nearly treeless Great Valley of California divides 



126 FOREST PHYSIOGRAPHY 

the Pacific forest into an eastern and a western section. The well- 
watered Sierra Nevada in the east has a heavy forest growth of sugar 
pine, red fir, yellow pine, and hemlock besides the famous Sequoia 
gigantea. The dry Columbia Plateaus have a discontinuous forest in 
which pine and larch are the most important types. The Great Basin 
region is still drier and supports an even more limited growth of pine 
and juniper at the lower elevations, and a scanty growth of fir and 
spruce at the higher elevations. 

The Rocky Mountains forest extends from the borders of the sur- 
rounding plains and the intermont basins up to elevations of 9000 to 
11,000 feet and is much broken into forest islands by the restricted 
areas of mountain land which are suflSciently high to provoke an ade- 
quate rainfall from the prevailing westerly winds. Spruce grows luxu- 
riantly at elevations ranging from 8000 to 10,000 feet, and at lower 
altitudes yellow pine, red fir, and white fir are abundant. This growth 
is characteristic of the Rockies as far south as New Mexico, where the 
lower elevations of the mountains of the Trans-Pecos region cause the 
forest to disappear or to become restricted to a few higher ranges such 
as the Sacramento and Davis Mountains of western Texas and eastern 
New Mexico. 

Two small forest tracts of exceptional character deserve mention in 
even this brief description. In Florida the subtropical climate has given 
rise to an Antillean type of flora among which mahogany, royal palm, 
and mangroves are of chief interest. The second tract is in southern- 
most Texas, where vegetation occurs whose affinities are with the 
Mexican flora. 



CHAPTER X 

COAST RANGES 

The relief of the relatively dry western half of the United States has 
a high importance in the distribution of the forests because of the 
effects of relief upon two of the controlling factors of forest growth — 
temperature and rainfall. We shall therefore begin our consideration 
of the physiography of the United States by a study of the West. Of 
the 190 million acres of national forests, more than 185 million occur 
west of the eastern front of the Rockies, a fact that further increases 
the forester's interest in the topography, drainage, soils, and rainfall 
of this vast region. 

Subdivisions 

The Coast Range system of mountains in the United States extends 
from southern California to the Straits of Juan de Fuca. The moun- 
tains of the system do not have uniform topographic qualities through- 
out but consist of four somewhat dissimilar sections. The southern 
section extends from southern California to the 40th parallel; farther 
north are the Klamath Mountains, which extend from the 40th to the 
43d parallel; the third section embraces the low Coast Ranges of western 
and northwestern Oregon; the fourth includes the Olympic Mountains, 
which rise to heights of over 8000 feet and are the highest mountains of 
the system next to those in southern California. 

Coast Ranges of California 

The Coast Ranges of California terminate on the northern margin 
of Humboldt County (p. 141); beyond them to the northeast He the 
Klamath Mountains, which are more closely alHed to the Sierra Nevada 
Mountains than to the Coast Ranges in rock character and geologic history 
though not in geographic position. The Coast Ranges of CaHfornia are 
sometimes regarded as ending on the south in Santa Barbara County, 
there giving way to the mountains of southern California. We shall 
here include the mountains of southern California with those of the 
coast of California to the 40th parallel in a single coast group because 
of (i) the extension of the tectonic Hnes of the northern mountains into 

127 



128 FOREST PHYSIOGRAPHY 

the mountains of southern California and (2) the closely related fact that 
the movements along these lines — movements to which the larger topo- 
graphic features are due — date in both cases from the close of the Tertiary. 
A unity of both structural and topographic characters is thus given the 
entire group of ranges. The group is divided, however (largely on the 
basis of trend), into three subgroups: (i) the Coast Ranges proper; 
(2) a broad chain extending from Santa Barbara County to the eastern 
and southeastern side of the Colorado desert, with a general trend west- 
northwest, and including the San Rafael, Santa Ynez, Santa Susannah, 
Santa Monica, and San Gabriel ranges, a chain parts of which are 
known locally as the Sierra Madre, though the application is neither uni- 
form nor clear; and (3) the mountainous country of the Valley of southern 
California. The principal ranges of this group are the northwestward- 
trending Santa Ana and San Jacinto mountains, sometimes called the 
Peninsular chain. ^ 

On both the north and the south the Coast Ranges are from 5000 
to 8000 feet high; the elevations of the central portions are from 3000 
to 4000 feet. San Lucia Peak, the highest peak of the central Coast 
Ranges, is less than 6000 feet high. In general the crests range from 
2000 to 4000 feet. 

The eastern margin of the Coast Ranges of California rises abruptly 
from the floor of the great central valley of California as a well-marked 
continuous mountain front. At its southern end it is a dissected fault 
scarp; elsewhere a smaller amount of faulting has taken place, but every- 
where the eastern border represents a line of strong deformation. In 
a broad view the western margin of the Coast Ranges is not at the 
shore line but at the edge of the continental platform on the 600-foot 
submarine contour, where the sea bottom changes its slope abruptly 
from a previously gentle incline and plunges steeply down to depths of 
8000 feet and more.- At the foot of this steep decline the sea bottom 
again assumes low gradients. The slope constitutes a notable moun- 
tain front rising from the floor of the Pacific and forming the natural 
western boundary of the coast system of mountains. It is interpreted 
as a great submarine fault scarp or series of fault scarps comparable to 
those that form the eastern front not only of the Coast Ranges of Cali- 
fornia but also of the Sierra Nevada. At the base of the steep sub- 
marine scarp, dredgings (Tuscarora explorations) at the depth of 12,000 
feet have brought up fragments of bituminous shale which are con- 

i A. C. Lawson and others, Section on Geology, The California Earthquake of April i8, 
1906, Carnegie Inst., vol. i, pt. i, pp. 2, 3 et al. 

2 Andree's Handatlas, bathymetric chart. No. 157. 



COAST RANGES 



129 



GEOMORPHIC MAP 
OF 

CALIFORNIA 

SHOWING THE DIASTROPHIC 

CHARACTER OF THE RELIEF 

AND THE MOST IMPORTANT 

KNOWN FAULTS 




Fig. 24. — Map of California. The heavy lines indicate the principal faults. 



130 FOREST PHYSIOGRAPHY 

sidered to be talus debris of so recent origin as not yet to have been 
buried by oceanic sediments. 

The coastal scarp above sea level is not everywhere regular in de- 
velopment; the most noticeable interruption is the Bay of "Monterey 
and adjacent slopes, which form parts of a syncHnal trough whose axis 
is at right angles to the trend of the coast and of the Coast Ranges as a 
belt. A second interruption of the continuity of the coastal scarp is 
at the Golden Gate and is due to a depression of the Coast Ranges 
which resulted in the drowning of the lower portions of land valleys 
that formerly crossed the coastal mountains. The Point Rees penin- 
sula is a third important break in the continuity of the coast line of 
California and is due to the manner in which the depression east of the 
ridge forming the peninsula has been drowned; the northern end of the 
valley is occupied by Tomales Bay, the southern by Bolinas lagoon.^ 

The Coast Ranges of California consist on the whole of a series 
of parallel ridges composed of sedimentary strata (Cretaceous- and 
later) that have been deformed on broad lines by deep-seated causes. 
There has been crumpling of the strata besides a certain amount of 
igneous eruption, but the major features are due to the effects of great 
dissection and later block faulting on a large scale, attended and fol- 
lowed by erosion. The character of the relief is in many cases markedly 
diastrophic and the relief features commonly have the rectilinear qual- 
ity associated with pronounced faulting, which also explains to a large 
degree the parallelism of the ridges. Examples are Castle Rock Ridge, 
Cavilan range, the Santa Cruz range, and many others whose borders 
are marked by the San Andreas fault, the Castle Rock fault, etc., which 
during the California earthquake of 1906 were the loci of maximum 
earthquake intensity.^ 

The most important line of faulting in the Coast Ranges of California 
is the Rift, as it has been termed, or the San Andreas Rift, a name 
taken from the San Andreas valley of the peninsula of San Francisco. 
The Rift is a continuous topographic depression for at least 190 miles 
from Point Arena to San Juan, and in this part of its course is nearly 
straight, following an old line of seismic disturbance which has a much 
greater extent — that is to say, from southwest of the Point to southern 
California, or about 600 to 700 miles. Indeed the Rift may extend 
much farther to the south and may be associated with the origin of the 

1 Lawson, loc. cit., pp. 12-15. 

2 For geologic time names consult Appendix D. 

5 Atlas of maps and seismographs accompanying the Report of the State Earthquake In- 
vestigation Commission upon the California Earthquake of April 8, 1906, Maps i, 22, and 23. 
Also the Santa Cruz quadrangle, U. S. Geol. Surv. 



COAST RANGES 131 

Colorado desert and the Gulf of California. The physical habit of the 
Rift valley, for example in the Bolinas-Tomales section, is that of a 
remarkably straight depression, with the southwestern wall steep, the 
northeastern wall gentle. The character of a pronounced topographic 
depression, however, is not everywhere sustained. 

The southern end of the great Rift may be traced for an unknown 
distance along the base of the mountains bordering the Salton Basin 
upon the northeast, where it probably dies out gradually. It is coin- 
cident with long and narrow valleys whose orientation is controlled by 
faulting along the Rift but whose detailed features are in large measure 
determined by erosion upon the exposed edges of formations of varying 
hardness. The depressions which constitute the major Rift along the 
southern margin of the Mohave desert appear to be almost wholly 
diastrophic. The steep northern flank of the San Rafael and San Gabriel 
ranges on the south side of the Mohave desert are degraded fault scarps, 
the walls of the great Rift valley. The exact share in all these vari- 
ous sections of the Rift valley that may be ascribed on the one hand to 
crustal deformation of the fault block t^-pe and on the other to erosion 
has not been determined. For miles at a stretch the earth on one side 
or the other of the fault in the southern part of the Coast Ranges has 
sunk in such manner as to give rise to basins and cliffs measured in 
terms of several hundred feet. 

The individual ridges of the Coast Ranges of California have a pro- 
nounced parallelism in a direction somewhat oblique to the main trend 
of the coast, so that they tend constantly to emerge upon the coast 
in the form of northwestward-trending peninsulas. The courses of the 
longitudinal valleys correspond either to the strike of the rocks or the 
trend of the fault lines and are oblique to the general trend of the coast 
range belt. The general drainage is therefore termed subsequent, for 
the streams have extended themselves along belts of weak rock or along 
fault depressions at the expense of an earlier drainage crossing the 
region in a westerly direction or transverse to the structure. Short sec- 
tions of the streams cross the ridges in steep-sided valleys or gorges, and 
these only may be termed antecedent.^ 

The tops of the ridges in some respects are more or less flat and pre- 
sent the character of a rolling, mature upland; but more commonly 
they are determined by the intersection of the slopes of adjacent valleys; 
even in the latter case, however, it is generally true that the ridge crests 
over wide areas reach about the same altitude and in a broad view give 
the impression of an upland with fairly uniform elevations and gentle 

1 Lawson, loc. cit., p. 20. 



132 FOREST PHYSIOGRAPHY 

slopes. The stream valleys, cut below the level of the dissected upland, 
are usually wide-bottomed in the softer and narrow-bottomed in the 
harder rocks. ^ 

The Santa Lucia Range illustrates many of the general features of 
the region. It is the dominant mountain range of the coast of Cali- 
fornia for over loo miles between latitude 35° and 36°3o' N., Fig. 24. 
For much of this distance it rises boldly from the Pacific Ocean and forms 
the most picturesque portion of the California coast. In places the 
spurs of the range terminate in cliffs several hundred feet high; in other 
places the range is bordered on the seaward side by a gently sloping 
platform or terrace which is from 40 to 80 feet high on its cliffed outer 
margin and 100 feet high on its inner margin. This platform is primarily 
a wave-cut terrace, though its surface is thinly covered with w^ash from 
thei. bordering hills.^ The Santa Lucia Range has an even sky Une many 
miles long, and a summit from 2 to 4 miles wide. Its regular front 
is a bold, compound, fault scarp. The range is traversed by narrow 
canyons which open out headward into broad valleys in an advanced 
stage of topographic development. In this respect the range resembles 
many others among the Pacific mountains. An earher surface, in some 
places softened and subdued with moderate waste-covered slopes, in 
other places a true peneplain, was deformed by faulting. The summit 
levels of the uplifted fault-blocks (the present ranges) display remnants 
of the ancient smoothly-contoured surface in strong contrast to the steep 
borders of the ranges sharply outlined by more recent faulting and now 
in process of vigorous dissection. 

Large portions of the Coast Ranges are unknown even through re- 
connaissance surveys. Among the known portions the Santa Cruz 
section between San Francisco Bay and the Bay of Monterey presents 
features of special interest. Here the parallelism of the valleys and 
ridges is apparent in the larger features of the topography but is less 
marked or absent in the minor relief. The main ridges have a steep 
northeast slope bordered by a series of valleys lying along the San 
Andreas Rift. The lines of the major folds of the Santa Cruz region 
are marked by more or less continuous valleys, and in the case of both 
these larger valleys and the main ridges the topographic and geologic 
features are in sympathetic relation.^ The hillsides of the region are 
generally covered with a deep coating of soil, and cliffs are rare, owing 
both to the friability of most of the rocks and to the advanced state 

1 Lawson, loc. cit., p. 20. 

2 H. W. Fairbanks, San Luis Folio U. S. Geol. Surv. No. loi, 1904, p. i. 

3 Branner, Newsom, and Arnold, Santa Cruz Folio U. S. Geol. Surv. No. 163, 1906, p. i. 



COAST RANGES 



133 



of topographic development which was reached before the last and 
recent uplift. An unusual feature of the topography of the Santa Cruz 
region is the occurrence of very steep yet soil-covered hillsides; 35° to 40° 
slopes are not uncommon, and in one place is found a soil- and vegeta- 
tion-covered hillside with a slope of 50° from the horizontal. There is 
a dense growth of timber and underbrush over much of the area, which 
does not prevent the thick covering of soil from being frequently in- 
volved in landslides in the belts of greatest faulting and folding.^ 

The Coast Ranges of northern California include, besides the moun- 
tains proper, a coastal tract which was eroded (Pliocene) to the form of 
a peneplain. The coastal peneplain was then uplifted and its streams 
intrenched; it now forms a dissected plateau with long and roughly 
level-topped ridges separated by equally long, narrow valleys. The ridges 
are remarkably constant in general altitude, and the sky line is essen- 
tially level. In a general perspective the view is that of a plain or 
sloping plateau of low relief. The peneplain was uplifted to an ele- 
vation of 1600 feet above the sea on the seaward margin, and to 2100 
feet on the inner margin. The mountainous tract adjacent on the 
east participated in the same movement. In Humboldt County several 
sharp peaks rise abruptly above the general level of the dissected 
plateau to 4000 or 5000 feet, but they are clearly encircled by remnants 
of the plateau which give to the mid-slopes of the peaks a distinctly 
terraced aspect. The peneplain may be followed in among clusters 
of mountain peaks and ridges and extends at least as far as the Bear 
River ridge. That the present dissected plateau was once a peneplain 
is inferred from the facts that the rocks composing it are of varying 
ages and of varying degrees of hardness, and that the general surface 
of the region bevels rather evenly across the deformed strata. On 
the summit of some of the ridges of the plateau numerous water-worn 
pebbles have been found, at 1600 feet, which are reasonably interpreted 
as remnants of larger bodies of stream gravels formed upon an erosion 
surface.^ 

The coastal peneplain grades into a region of stronger rehef on the 
east where the stream courses were still completely under the control 
of geologic structure at the end of the first erosion cycle and flowed in 
mature subsequent valleys which were inherited by the streams of the 
second or present cycle of erosion. The abrupt coastal margin of the 
uplifted peneplain of northern California has given rise to a youthful 

1 Branner, Newsom, and Arnold, Santa Cruz Folio U. S. Geol. Surv. No. 163, 1906, p. 10. 

2 A. C. Lawson, The Geomorphogeny of the Coast of Northern California, Univ. Cal. Bull., 
Dept. Geol., vol. i, pp. 242-244. 



134 



FOREST PHYSIOGRAPHY 



topography along the coast; the coastal canyons are narrow and precipi- 
tous, and V-shaped profiles predominate. In the middle stretches of 
the streams degradation is less intense and the topography appears 
somewhat less rugged. 

Recent events following the uplift and dissection of the coastal pene- 
plain of California are a subsidence of at least 370 feet at the mouth of 
the Sacramento River which flooded the lower portions of that valley 
and gave rise to the magnificent harbor of San Francisco. The drowned 
mouth of the river once discharging across the Coast Ranges at this 
point is known as the Golden Gate. The last episode in the region 
has been a slight uplift in the vicinity of the Straits of Carquinez.^ 




Fig. 25. — Coastal terraces produced by wave erosion, west of Santa Cruz, California. (U. S. Geol. Surv.) 

The uplift of the coastal peneplain of northern California was not 
accomplished in a single continuous movement but was interrupted 
by many halts. During these periods of relative stability there were 
formed well-developed ocean terraces which are among the most promi- 
nent features of the coastal topography. Such terraces were always 
involved in later uplifts and now stand at high levels, the highest 
representing the algebraic sum of all coastal changes whether of uphft 
or depression since the beginning of the last series of changes in the 
level of the land. The highest terrace of northern California is about 

1 A. C. Lawson, The Geomorphogeny of the Coast of Northern California, Univ. Cal. Bull., 
Dept. Geol., vol. i, pp. 270-271. 



COAST RANGES 135 

1500 feet above sea level. Below this are prominent terraces at 1400, 
1 180, 760, 440, 350, and 280 feet, respectively, above sea level, with 
many less prominent terraces at intermediate levels. The lower terraces 
have all the characters associated with wave and current origin, such 
as a rather regular seaward slope, upturned strata smoothly planed off, 
residual stacks, beach bowlders, and sea cliffs with horizontal base lines. 
The higher ones are usually not so clear, though even the highest have 
sufficient definition in the form of sea cliff, sloping terrace, and bowlder 
beach to make its character certain.^ 

MOUNTAINS OF SOUTHERN CALIFORNIA 

In the southernmost division of the coastal mountains of California 
(see p. 127) faults have also played a very important part in the topog- 
raphy. Both the northern and southern sides of the San Gabriel range 
are determined by a profound fault; the range may be interpreted 
as a horst thrust up between two bounding faults. Since uplift the 
range has been thoroughly dissected and older surfaces of erosion 
destroyed. 

" One seeks in vain for horizontal lines along the San Gabriel tops; a confusion of peaks and 
ridges of discordant and seemingly unrelated heights makes up the mountain mass. . . . [They] 
present a labyrinth of canyons and ridges and peaks, with no level areas of any size. The 
ridges have narrow summits; the peaks are sharp; the streams are all evenly graded from 
source to mouth." 2 

The Santa Ana Mountains are a tilted, seaward-sloping mountain 
block with a very straight and abrupt fault scarp that faces the north- 
east and overlooks the Ferris plain. The block is an elevated and as 
yet but little dissected peneplain (Cretaceous) with remnants of younger 
(Tertiary) deposits upon it, indicating that it has in part at least been 
resurrected in recent times from a buried condition. It is thought that 
the same tilted block structure extends beyond the Santa Ana Mountains 
southward to the international boundary and even beyond. Both sides 
of the San Jacinto Mountains are precipitous and probably determined 
by faults, so that the ridge has very bold margins. 

Among the drainage features of these mountains are the interesting valleys of the Santa Ana 
and Santa Margherita rivers which are antecedent to the tilting of the region; they persisted 
in their southwestward courses during the development of the fault scarps, and now cut squarely 
across the range, draining the valley lands on the northeast.' 

1 A. C. Lawson, The Geomorphogeny of the Coast of Northern California, Univ. Cal. Bull., 
Dept. Geol., vol. i, pp. 246-247. 

2 W. C. Mendenhall, Groundwaters and Irrigation Enterprises in the Foothill Belt, South- 
ern California, Water-Supply Paper U. S. Geol. Surv. No. 219, 1908, p. 17. 

3 A. C. Lawson and others, The California Earthquake of April 18, 1906, Carnegie Inst., 
vol. I, pt. I. pp. 23-24. 



136 



FOREST PHYSIOGRAPHY 



SAN BERNARDINO RANGE 

The San Bernardino range of southern California is a distinct topo- 
graphic unit and does not have a close genetic relationship with the other 
members of the Coast Range System in southern California. It is 
much younger than the San Gabriel range and appears to have had 
a history different from that of the San Jacinto range south of it. 
The relief of the mountains is outlined upon an uplifted fault block 
once of somewhat more regular development than at present. Rem- 
nants of an old surface of moderate relief, broad elevated valleys, 




Fig 



26. — Redlands and San Bernardino and San Gorgonio Peaks, San Bernardino Mountains, Cali- 
fornia. (Mendenhall, U. S. Geol. Surv.) 



plateau-like ridges, and several interior basins like those in the Mohave 
desert on the north, are the principal secondary topographic elements. 
At its western end is displayed a long even sky line at elevations 
between 5000 and 6000 feet above the sea. 

"... there are many wide upland valleys, forested and grassy glades, and lakes or playas 
like Bear Lake and Baldwin Lake. Where these upland levels are attained it is difEcult to 
realize that one is actually in the high mountains. The surrounding topographic forms are 
rounded and gentle, the level areas are extensive, the streams meander placidly through broad 
meadows, and the topographic type is that of a rolhng country of moderate elevation. But 
as the edge of these interior uplands is approached the streams plunge into precipitous canyons, 
the slopes are as steep as earth and rock can stand, the roads and trails twist and turn and 
double to find a devious and precarious way to the valleys below." 1 

1 W. C. Mendenhall, Ground Waters and Irrigation Enterprises in the Foothill Belt, South- 
ern California, Water-Supply Paper U. S. Geol. Surv. No. 219, 1908, p. 17. 




V00(i>\ 



Scale of Miles 



K 1 2-3 i 

Contour interval 500 feet 



Fig. 27. — Bear Valley and the adjacent country exhibit the sub- 
dued relief characteristic of the interior of the San Bernardino 
Mountains. The parallel of 34° 20' coincides with a fault 
scarp on the northern border of the range; the southern edge of the map represents a part of the southern 
border of similar origin. Both borders are deeply dissected. Note the withering streams, foreland 
plain, and playa of the Mohave desert. (San Gorgonio quadrangle, U. S. Geol. Surv.) 

137 



138 FOREST PHYSIOGRAPHY 

The mountain mass was blocked out of a portion of the earth's crust 
that was at one time continuous with the Mohave desert region and the 
San Bernardino Valley. The highest portion of the range is a rather 
sharp ridge about six miles long culminating in San Bernardino Moun- 
tain (10,630 feet) on the west and San Gorgonio Mountain (11,480 feet) 
on the east. 

A surprising feature of the topography of the range is the occurrence 
of glacial cirques, moraines, and basin-like depressions. The southern 
limit of glaciation in this longitude has until lately been thought to be 
somewhat farther north, so that this occurrence of glacial features is 
one of the southernmost in the country.^ Both the northeast and the 
northwest slopes of the main ridge appear to have been glaciated, the 
snowy accumulations having been formed in alcoves near the summit 
where drifted snows still gather. At the head of Hathaway Creek are 
five semicircular terminal moraines a mile and a half below the cirque-like 
basin close under the crest. Of interest in this connection is the fact 
that the summit of the range still contains a distinctly boreal fauna 
and flora. 2 

The Klamath Mountains 

In the second major division of the Coast Ranges dominated by the 
Klamath Mountains and designated the Klamath sub-province there are 
three well-marked subdivisions: (i) a narrow coastal plain, (2) high 
marine terraces, and (3) a well-dissected plateau. 

The coastal plain is from one to five miles wide, and its inner margin 
stands several thousand feet above the sea. Swamps border the ex- 
panded lower courses of the streams where lagoons have been formed 
back of the sand reefs that fringe the coast. An interesting feature 
of portions of the coast is the variable position of the stream mouths . 
through the year; the south and southwest storms of winter produce a 
coastal drift northward and the inlets through which the rivers dis- 
charge are moved in this direction; but when the northwest winds of 
summer prevail the movement is southward. In many places the winds 
have blown the reef sands into dunes whose shifting character may long 
prevent tree growth. There appears to be a natural limit to this action, 
however, for each locality, so that ultimately lower forms of vegetation 
take hold of the sand and bind it, allowing the trees to come in. The 

1 Other southerly localities where glacial features have been found are (a) near Santa Fe, 
(b) on San Francisco Mountain, (f ) near Nogales, etc. For a resume of these occurrences see 
D. W. Johnson, The Southernmost Glaciation in the United States, Science, n. s., vol. 31, 
1910, pp. 218-220. 

2 Fairbanks and Carey, Glaciation in the San Bernardino Range, California, Science, n. s., 
vol. 31, 1910, pp. 32-33. 



COAST RANGES 139 

action is well illustrated along the inner margin of some of the dunes 
near Coos Bay, Oregon. Locally dunes have been driven inland so far 
from the source of sand supply, a mile or more, as at last to make little 
progress and to become covered with a forest growth. 

On its inner margin the coastal plain has been moderately dissected; 
the outer margin of the plain still bears marks of extreme youthfulness 
in the form of coastal lagoons and recent marine sediments. Occasional 
rock stacks persist, of which Tupper Rock is a conspicuous illustration; 
they represent harder or more favorably located rock masses that with- 
stood the wave erosion which carried away the softer surrounding rocks. 
Although the coastal plain of this part of Oregon is narrow it contains 
by far the greater part of the people of the region, a fact due to its fiat 
tillable surface and the dark, rich loam which favors the interests of 
agricultural people. 

The ascent from coastal plain to high-level plateau is made by a 
series of terraces sculptured upon the prominent spurs that define the 
interfluves. Ancient sea cliffs with ancient beaches at their foot alter- 
nate with long gentle slopes marking the wave-cut terraces that once 
extended seaward from the cliff as a submarine platform. The ter- 
races range in height from 500 to 1500 feet. At the latter elevation 
is a well-marked, though discontinuous, sea cliff which has been traced 
for many miles along the coast. The preservation of these old cliffs and 
benches of a former shore line at such high elevations above the sea 
are suggestive of the rapidity that characterizes uplift on these shores. 

The Klamath Mountains proper embrace all those peaks and ridges 
lying between the 40th and 43d parallels. Some of their most con- 
spicuous members are the Salmon, Trinity, and Scott mountains of 
California and the Siskiyou and Rogue River mountains of Oregon. 
The mountains are composed in large part of rocks similar to those 
found in the Sierra Nevada, — limestone, sandstone, shale, schist, diabase, 
etc., — with traces here and there of lavas having a close relationship 
to those of the Cascade Mountains; in late physiographic history and 
in geographic position, however, they are related to the Coast Ranges.^ 

The dominating physiographic feature of the Klamath sub-region is 
the Klamath plateau. From one of the higher summits a general view 
of the landscape may be obtained which shows that while there are 
many small irregularities, the summit levels approximate a general plane 
with moderate inclination toward the sea. The elevation of the plateau 
is from 2000 feet on the west to 4000 and 5000 feet and more on the 
east. In many places decidedly flat summits may be noted, so that in a 

1 J. S. Diller, Roseburg Folio U. S. Geol. Surv. No. 49, 1898, p. i. 



I40 FOREST PHYSIOGRAPHY 

general view the surface appears to be a practically level-topped plateau 
deeply trenched by streams. The South Fork range in Trinity County, 
Oregon, has an even sky line more than 40 miles long at an elevation 
exceeding 5000 feet in spite of its variable structure. Such ^a relation 
of surface to structure is indicative of a long erosion period in which 
rocks of diverse altitudes, hardnesses, etc., were brought to essentially 
the same level; in short, that the region was peneplaned, that is, re- 
duced by long-continued erosion at one level to the form of an almost 
featureless plain. Uplift is indicated not only by the relativel}^ high 
level at which the plain, once formed at sea level, now stands, but also 
by deep dissection. 

The fact of early peneplanation and later dissection is also well shown 
by a comparison of the upper and lower valley slopes. The lower por- 
tions of the valleys are in general narrow and canyon-like, with prevail- 
ingly steep descents, while the upper portions of the valleys are wide 
and the slopes gentle. The upper gentle slopes are the slopes of an 
early valley system which is now being destroyed by the present drainage 
cut far below the old level since the uplift of the region. One of the 
best preserved of the early valleys is the Pitt River valley. The level of 
the broad, shallow, old valley of the Pitt is but 500 feet below the flat 
backbone of the ridges across which its course is directed, and is in very 
strong contrast to the deep, narrow, canyon-like valley of the present 
river. Traces of earlier valleys may also be found on the uplands along 
the McCloud and Little Sacramento valleys. ~ 

An interesting fact which bears upon the origin of the older valleys 
and the former existence of a peneplain is the occurrence at Potters 
Creek cave of the bones of some forty species of animals of which at 
least seventeen, including the mastodon, elephant, and tapir, are ex- 
tinct. The character of the fauna indicates low relief and a condition 
quite out of harmony with the present topography.^ The low relief that 
must have existed here when the peneplain was nearing its latest stages 
of development is also indicated by the fine character of the correspond- 
ing sediments (lone formation) which like the characters of the fossil 
flora and fauna suggests a flat coastal region whose climate was not 
notably different from that of Florida to-day.- 

The Klamath peneplain in an uplifted and deeply dissected state has 
been traced southwestward to the head of the Sacramento Valley, Califor- 
nia, where the slopes of the mountains become gentler as they approach the 

1 J. S. Diller, A Preliminary Account of the Exploration of the Potters Creek Cave, Shasta 
County, California, Science, n. s., vol. 17, 1903, pp. 708-712. 

2 J. S. Diller, Redding Folio, Cal. U. S. Geol. Surv. No. 138, igo6, p. 10. 



COAST RANGES 



141 



highest summits. These flattish crests approximate a general plain and 
indicate that the region was one of gentle relief before the last uplift. 
Turning now to the more rugged interior portions of the Klamath 
district we find that the main ranges fall into two rather well-defined 
systems which cross each other nearly at right angles. The most 




Scale of Miles 
6 5 lb 20^ Jo 

Fig. 28. — Boundaries between the Sierra Nevada, Cascades, Coast Ranges, and the Klamath Moun- 
tains. The Lassen Peak volcanic ridge extends from the Pitt River on the north to the North Fork 
of the Feather River on the south. It is the southern part of the Cascade Range. Goose Lake dis- 
charges into Pitt River only at long intervals. (After Diller, U. S. Geol. Surv.^ 



prominent ranges have an east-west trend, as the Rogue River, Siskiyou, 
Scott, and Trinity; on the other hand the Yallo Bally, Bally Choop, 
South Fork, and Salmon River mountains and many less important 
ridges run approximately in a northerly direction. Even in the central 



142 FOREST PHYSIOGRAPHY 

portion of the group, as between the Rogue River and the Trinity valleys, 
the north-south trends are apparent. 

The mountain-rimmed basins of the region have two characteristic 
features; all receive the drainage of comparatively large areas, 'and each 
is drained by a main stream that leaves the basin to cross a bordering 
range through a deep canyon. Scott Valley, for example, 8 by 25 miles 
in extent, has a nearly level floor, and an extensive system of centripetal 
tributaries; it drains through an almost impassable canyon more than 
20 miles long. Other interior valleys of this type are Hay Fork, Trinity, 
and Illinois. 

It seems clear from the persistent manner in which the ranges lie 
athwart the main drainage lines that the ranges were developed after 
the drainage had become well established. It is conceived .that the 
eastward-trending ranges had been developed, peneplanation had been 
accomplished, and the streams by gradual development had gained 
courses westward to the sea when elevation along north-south axial lines 
deformed the peneplain and gave rise to a system of cross ranges with 
intervening structural valleys and valley basins.^ 

The deformations of the Klamath peneplain were sufficiently acute 
to cause the north-south ranges to stand well above the general level of 
the broadly uplifted portions of the peneplain. The east-west ranges in 
the higher and more rugged portions of the Klamath group have a 
residual relation to the uplifted and dissected peneplain about them. 
They represent unreduced elevations and display a boldness of form 
and an irregularity of relief in sharp contrast to the plateau character 
of the marginal tracts of the region. They are nowhere lofty, however, 
nor does their ruggedness in any place have alpine characteristics. In 
general their elevation exceeds the elevation of the bordering peneplain 
from 2000 to 4000 feet. 

Coast Ranges of Oregon 

The Coast Ranges of Oregon constitute the third member of the 
Coast Range System of mountains. Their geology and geography have 
not yet been studied in sufficient detail to make generalization very 
profitable. It is known that they consist in part of sandstones (Eocene) 
and in part of volcanic rocks, the latter type constituting a considerable 
part of the ranges south of the Columbia River.^ In the Coos Bay 
region a portion of the Coast Ranges of Oregon has been described as 

1 F. M. Anderson, The Physiographic Features of the Klamath Mountains, Jour. Geol., vol. 
10, 1902, pp. 144-159. 

2 Willis and Smith, Tacoma Folio U. S. Geol. Surv. No. 54, i8gg, p. i. 



COAST RANGES 143 

exhibiting somewhat flat though narrow hill and ridge crests from 
which steep slopes descend to the valley floors.^ Farther north 
similar qualities are exhibited, and in addition there are a number of 
rather flat-topped tablelands which represent remnants of an elevated 
peneplain. The even summits rise to maximum heights from 1200 to 
1700 feet above the sea south of the Columbia River. Above them 
are upper mountain slopes and a considerable number of peaks against 
which the plain breaks abruptly. The peaks form true monadnocks 
among which Saddle Mountain displays typical features and relations.^ 

While there is great variability in rock hardness from point to point it 
is notable that in general the rocks are so soft as to permit rapid erosion 
wherever the forest is removed. Under natural conditions erosion is 
prevented by an extremely dense vegetal covering which not only breaks 
the force of the heavy rains but also binds the soil and delays run-off in 
other familiar ways. 

The Coast Ranges of southwestern Oregon almost meet the western 
spurs of the Cascades. The Willamette Valley narrows toward its head, 
and beyond it and to the south are other streams of still more restricted 
valley development. At Roseburg (43° 10'), the depression between the 
ranges narrows to but fifteen miles. The foothills of the Cascades form 
a prominent though not a precipitous mountain border. The streams 
descend from the long, sloping western flank of the volcanic tableland 
of the Cascades and emerge from their rugged canyons to enter the 
more open val'ey stretches of the Umpqua, or Rogue, or Klamath rivers. 
Among these valleys the Umpqua alone lies north of the Klamath 
Mountains. It maintains an open character for but a short distance, 
however, then strikes boldly into and across the Coast Ranges, where 
its valley becomes a canyon. The most remarkable feature of the 
canyon is its winding course, which appears to represent the meander- 
ings of its stream in an earlier topographic cycle when it flowed upon 
the surface of a peneplain now represented by the even and accordant 
crest lines of the Coast Ranges. The courses of the master streams, as 
the Nehalem in northwestern Oregon, resemble the Umpqua in the 
manner in which they cut across the mountains. They gained their 
courses on the coastal peneplain and since its uplift to form the Coast 
Ranges they have persisted in their courses. The smaller streams all 
show a sympathetic relation to the structure; their valleys in general 
follow the outcrop of the softer rocks. 

* J. S. Diller, Coos Bay Folio U. S. Geol. Surv. No. 73, igoi, p. i. 

2 J. S. Diller, A Geological Reconnaissance in Northwestern Oregon, 17th Ann. Rept. U.S 
Geol. Surv., pt. i, 1895-96, pp. 449, 488. 



144 FOREST PHYSIOGRAPHY 

The eastern front of the Coast Ranges of Oregon is a bold, partly dis- 
sected fault scarp, about 2000 feet high, formed of massive sandstone 
which stands above the lowland developed upon the shales and thin- 
bedded sandstones east of it. The mountain spurs running, westward 
to the sea have a longer and gentler descent than those extending east- 
ward to the Willamette Valley. The western spurs terminate on the 
coast as prominent and cliffed headlands connected by stretches of 
sand beach covered with a dense growth of grass and ferns. 

Great terraces have been developed on the coastal margin of the 
Coast Ranges of Oregon just as on the western borders of the Klamath 
Mountains and the Coast Ranges of California. Since their development 
the terraces have been uplifted to heights of hundreds of feet, the highest 
attaining an elevation of 1500 feet. Above this elevation uniformity of 
level is less marked but still sufficiently marked to indicate the existence 
before the last uplift of an extensive plain of erosion now maturely and 
deeply dissected by the rejuvenated streams.^ 

Olympic Mountains 

The Olympic Mountains are the most conspicuous member of the 
northernmost section of the Coast Range System. They lie north of the 
Columbia River and west of Puget Sound. Like the Cascades the domi- 
nant peaks are volcanoes that rest upon a much older schistose rock. 
The highest peak of the Olympics, Mount Olympus, rises 8200 feet above 
the sea, and crowns a magnificent range in full view from the eastern 
side of the Sound. The higher mountains are alpine with sharp spires 
and serrate ridges from 6000 to 8000 feet high. The mountains have a 
roughly circular form and are about 40 miles across. The drainage of 
the region is radial, the streams being arranged much like the spokes of 
a wheel of which the region of high mountains is the hub ; it has been 
suggested that this feature is due to the domed warping of a former 
flatfish surface of erosion.- 

The uplift of the mountains is still progressing, or at least uplift has 
occurred in postglacial time, as shown by the gently folded and tilted gla- 
cial clays, sands, and gravels in the vicinity of Port Angeles. The range 
is one but little known to-day on account of the ruggedness of the 
coimtry, the fallen trees, the lichen-covered rock slopes, and the extreme 
density of the tangled underbrush. Because of the high degree of 
humidity, the great rainfall, and the equable and moderate temperature 

1 J. S. Diller, Roseburg Folio U. S. Geol. Surv. No. 49, 1898, p. 4. 

2 Ralph Arnold, Geological Reconnaissance of the Coast of the Olympic Peninsula, Washing- 
ton, Bull. Geol. Soc. Am., vol. 17, 1906, pp. 451-468. 



COAST RANGES 145 

the mountain slopes are clothed with an almost impenetrable forest up 
to an altitude of 7000 feet. The Olympic forest is the densest in 
Washington and with few exceptions the densest in the country. It 
consists chiefly of red fir and hemlock. 



Climate, Soil, and Forests 

The Coast Ranges extend through 20 degrees of latitude and lie in two 
distinct cHmatic belts, the belt of the westerly winds and the horse latitude 
belt. Southern California lies wholly in the latter belt, where the rain- 
fall is scant on the lowlands and limited on the highlands or mountains, 
yet suflScient on the higher exposed slopes to support a forest growth. 
Its forests are in general of small extent, although a number of districts 
in the coastal ridges and the San Bernardino Mountains have good 
stands of timber. The Forest Service estimates the total standing live 
timber of merchantable size in this district, at approximately i % of the 
total for the State. At present there is in some localities a tendency 
toward eucalyptus culture, which may eventually have a beneficial effect 
upon the run-off of the region,^ besides supplying the demand for a hard- 
wood, one of the great defects of the Pacific forests.^ It is, however, 
particularly sensitive to cold and especially will not endure frost, hence 
the range of its culture will be distinctly limited. 

The Coast Ranges south of San Francisco lie in the belt of winter 
rains and are almost rainless in summer months. Nearness to the sea, 
however, brings climatic responses of great importance to vegetation, 
even in summer. The regular northwest winds of summer blow from 
the sea and for several months are accompanied by cool, damp fogs 
which sweep inland forty to fifty miles. They temper the hot summer 
weather, depress the rate of evaporation, and in the lands they over- 
lie they make possible the production of certain crops without irri- 
gation. 

The larger part of the rainfall occurs on the western slopes of the 
westernmost ranges, decreasing on each range in eastward succession. 
It is nowhere sufficient to support a true forest vegetation, except im- 
mediately south of San Francisco where the Coast Ranges are covered 
with a heavy growth of timber and underbrush. At the heads of 
the valleys which drain the higher portions of the Santa Cruz Range 

1 Van Winkle and Eaton, Quality of the Surface Waters of California, Water-Supply Paper, 
U. S. Geol. Surv. No. 237, 1910, p. 65. 

2 Betts and Smith, Utilization of California Eucalypts, Circular U. S. Forest Service, 
No. 179, 1910, p. 6. 



146 



FOREST PHYSIOGRAPHY 




Fig. 29. — Distribution of western forests and woodlands. Solid black represents continuous forests; 
dotted areas represent woodland, that is, a thin scattered growth of forest vegetation. (Newell.) 

the rainfall is heavy and originally supported a dense growth of 
redwoods.^ 

Farther south, at San Luis Obispo (lat. 35° 20') the rainfall is 21 
inches, though it has the variable quality of the true desert type of 
rainfall, ranging in different years from 5 to 40 inches, a feature which 

I Branner, Newsom, and Arnold, Santa Cruz Folio U. S. Geo!. Surv. No. 163, 1909, 
pp. 9, II. 



COAST RANGES 147 

greatly limits the forest growth since in dry years only the most favored 
situations supply trees with the necessary moisture. The higher and 
steeper mountain ridges are generally covered with a dense growth of 
low shrubs or chaparral, among which are the manzanita, scrub oak, 
and California lilac. The sycamore follows the watercourses and is 
grouped about springs, in places forming dense groves. The canyons 
and marshy tracts have a growth of willow and laurel. In the higher 
valleys white oak is abundant, while the Digger pine is common on the 
ranges east of those on the immediate coast. 

There is great variation in the soils throughout the Coast Ranges of 
California and related variations are clearly traceable in many of the 
plant distributions. At San Luis Obispo heavy and rich soils support 
grasses and wild oats which replace the shrubby vegetation even on 
steep slopes. Live oak and laurel are found on areas where a rich soil 
and a good water supply are combined. Vegetation is most scanty where 
soils of poor quality occur, for example over areas underlain by ser- 
pentine rocks. The best growth of grasses is found on soil derived from 
an earthy sandstone (San Luis formation) intruded by basic rocks ; these 
yield on decay a deep, residual soil of great fertility even on steep 
hillsides.^ 

North of San Francisco the rainfall increases rapidly as one enters 
the belt of permanent westerly winds. While the rains are more fre- 
quent and heavy during the winter season they do not fail in summer as 
is the case farther south. In Oregon and Washington the Coast Ranges 
are heavily watered and receive more precipitation per unit area than 
any other tract in the country. At 2000 feet the Coast Ranges of north- 
western Oregon enjoy a total precipitation of 138 inches^ and at higher 
elevations the precipitation is estimated at 150 inches.^ While this 
enormous precipitation is not evenly distributed throughout the year 
the rainfall is heavy even in the relatively drier season, hence the forest 
growth is extremely dense and the trees of great size. Because of in- 
creasing temperature there is a marked increase in size with decreasing 
elevation in the well-watered portions of the mountains. 

These two primary controls of forest distribution, precipitation and 
temperature, have important variations in altitude and latitude that 
are well expressed in the Coast Range System of North America as a 

1 H. W. Fairbanks, San Luis Folio U. S. Geol. Surv. No. loi, 1904, pp. i, 2, 14. 

2 A. J. Henry, Climatology of the United States, Bull. Q, U. S. Weather Bureau, 1906, 
pp. 948-949- 

3 J. C. Stevens, Water Powers of the Cascade Range, pt. i. Southern Washington, Water- 
Supply Paper U. S. Geol. Surv. No. 253, 1910, p. 4. 



148 FOREST PHYSIOGRAPHY 

whole. In Alaska the greater portions of the mountains are bare or 
covered with snow fields and glaciers; in the Coast Ranges the forest is 
restricted to a belt between 2500 feet and sea level. In the interior 
mountains of Alaska, such as the Endicott Mountains, no' forests at 
all occur because of cold and at least physiological dryness. Farther 
south the cold timber line has a greater elevation and the forest belt 
is wider, attaining its maximum development in Washington, Oregon, 
and northern CaHfornia. Still farther south the dryness of the low^er 
slopes causes the forest growth to be restricted at lower elevations on 
account of drought, as it is restricted at higher elevations because of 
cold. Like the cold timber line the dry timber line lies at progressively 
higher elevations with decreasing latitude and increasing temperature, so 
that in southern California the forest growth is restricted to the upper 
slopes and summits in the zone of maximum rainfall. '^ 

The higher mountain slopes and mountain summits of Alaska are 
without forests; in southern California the plains and lower valleys are 
without forests. The mountain summits in the latter case are suf- 
ficiently warm to support forests, but the lower slopes are too dry. 
The intermediate tract has neither the great cold of Alaska nor the 
great dryness of southern California. Its forests of fir and cedar in 
Oregon and Washington and of redwood in northern California are 
among the most magnificent in the world. Broad-leaved trees are rare 
however. A few specimens are found along the streams and in the lower 
valleys, as the maple, Cottonwood, ash, and alder in Washington and 
the oaks in CaHfornia.^ The forest is composed chiefly of conifers, but 
within it there is considerable variation in the distribution of species on 
account of differences of soil, climate, and topography. The cedars 
thrive best in the moister valleys and along the watercourses, though 
their range includes a large extent of higher mountain slopes. The firs 
thrive on the drier (though in an absolute sense wet) uplands, ridges, 
and steep mountain slopes, but they are also tolerant of wetter situa- 
tions. On the steep declivities and sharp ridges, between 4000 and 
8000 feet, as well as in more favorable situations, the sugar pine is found ; 
in the middle of its range it attains great size and remarkable symmetry 
of form. 

I J. Hann, Handbook of Climatology, igo3, pp. 305-308, presents an important summary 
of knowledge concerning increase and decrease of rainfall with increasing altitude and discusses 
the altitude of the zone of maximum rainfall. Scarcely any observations of the elevation of 
the zone of maximum rainfall have been made on mountains in middle latitudes, but it is 
probably between 3000 and 6000 feet, varying with the exposure, the temperature, etc. 

' I. C. Russell, North America, 1904, pp. 238-239. 



CHAPTER XI 
CASCADE AND SIERRA NEVADA MOUNTAINS 



CASCADE MOUNTAINS 

Central Cascades 

The Cascade Mountains form a separate physiographic province not 
only because of the distinct manner in which their borders He above the 
surrounding country but also because of their characteristic interior 
features. The province is set off from the Sierra Nevada Mountains on the 
south, Fig. 28, by the valley of the North Fork of Feather River in north- 
eastern California; the northern Cascades terminate quite as sharply 
immediately north of the international boundary line and south of the 
Frazer River Valley. The western and eastern borders of the Cascades 
descend steeply to the Sound Valley and the Columbia Plateaus respec- 
tively. The eastern border of the Cascades is particularly well marked 
in central Washington and in Oregon immediately south of the Columbia 
River, where the steepness of the slopes suggests an origin through either 
very sharp folding or faulting, but faults have not been actually observed, 
for lava flows to a large extent conceal the underlying structure. 

Except for the breaks of the Columbia, Klamath, and Pitt valleys 
the Cascades possess marked continuity, and roads have been built 
across them only with great difficulty. Three railways cross the 
mountains to Tacoma and Seattle, but the grades are very steep and 
each line at the highest point requires a tunnel about a mile long. 

In the earlier descriptions of the Cascade Mountains great attention 
was paid to the line of lofty volcanoes that are dominating elements 
in almost every view. Conspicuous among these elevations are Mount 
Rainier (14,500), Mount St. Helens (9700), Mount Baker (10,800), and 
Mount Adams (9500) in Washington, and Mount Hood (11,200), Mount 
Jefferson (10,200), and Mount Pitt (9700) in Oregon. The early ex- 
planation of the Cascades, suggested by the fact that a large amount of 
volcanic material occurs in the region, ascribed their forms wholly to 
volcanic processes, but later studies^ show that the Cascades, at least in 

1 I. C. Russell, A Geological Reconnaissance in Central Washington, Bull. U. S. Geol. 
Surv. No. 108, p. 30. 

149 



I50 



FOREST PHYSIOGRAPHY 












Washington and north-central Oregon, have been 
formed not mainly by the piUng up of volcanic 
material but by the broad uplift and deformation 
of lava sheets, granites, and sedimentary strata. The 
great volcanoes that appear to be such prominent 
features of the range are secondary to the main 
mountain forms which consist of deeply intrenched 
valleys and sharp ridge crests with accordant alti- 
tudes. It has also been determined that the struc- 
ture of the range is highly complex and, that the 
conception of a warped monocli'nal fault block sculp- 
tured by erosion such as is properly applied to the 
Sierra Nevada requires considerable modification 
here.'^ On the basis of truncated folds and a general 
lack of sympathy between surface and structure over 
broad areas, it is concluded that the Cascades may 
be termed mountains of the second generation; that 
is to say they are mountains which have been formed 
by the broad uplift and deep erosion of an almost 
base-leveled or peneplaned surface." 
I" Perhaps the two best localities from which to 
I" observe that uniformity of summut levels which is an 
^ inheritance from the period of peneplanation are at 
g the head of Cold Creek, Washington, or near Cas- 
J cade Pass,^ although in many locahties within the 
.5 province, accordance of summit levels can not be 
3 observed because of (i) the complex nature of the 
S, later deformation that affected the ancient surface, 
^ (2) the volcanic outpourings that have in many 
.s places obliterated the old relief, or (3) the presence 
i of unreduced or residual masses. This is true espe- 
'c daily of the more elevated portions of the range 
a where no recognizable flat-topped remnants of the 
^ original plateau are to be found. ^ 

"o 

'° 1 I. C. Russell, A Preliminary Paper on the Geology of the Cascade 

Mountains in Northern Washington, 20th Ann. Kept. U. S. Geol. 
Surv., pt. 2, iSgg, p. 137- 

2 Idem, p. 140. 

3 Smith and Willis, The Physiography of the Cascades in Central 
Washington, Prof. Paper U. S. Geol. Surv. No. 19, Plates 9 and 10, 

PP- 53-54- 

i I. C. Russell, A PreUminary Paper on the Geology of the 
Cascade Mountains in Northern Washington, 20th Ann. Rept. U. S. Geol. Surv., pt. 2, p. 141. 



CASCADE AND SIERRA NEVADA MOUNTAINS 



151 




152 



FOREST PHYSIOGRAPHY 




p^ o 






CASCADE AND SIERRA NEVADA MOUNTAINS 



153 




154 FOREST PHYSIOGRAPHY 

The uniformity of summit level has been found to extend over the 
greater part of the Cascades, but it is clearly visible only from selected 
viewpoints and is generally expressed in the ideal plane of the ridge crests 
and the hilltops rather than in the few undissected remnants of the 
former plateau now remaining. It occurs at elevations varying from 
4000 to 8000 feet; the maximum of 8000 feet is attained north of the 
47th parallel and continues to the 49th parallel. In the vicinity of 
Mount Rainier the plateau remnants, at about 7500 feet, form the plat- 
form on which the cone of Mount Rainier stands. Toward the south 
the altitude of the plateau decreases and becomes about 4000 feet in 
southern Oregon where the width of the province -at the plateau level 
is from 60 to 75 miles. Between latitude 44° and 45° N. in the Mount 
Washington-Mount Jefferson country the accordance of summit levels 
among the hill and ridge crests is quite remarkable, the broad bases 
of the snow-capped peaks resting upon the general summit of the 
plateau as shown in Fig. 32. The plateau is at an elevation of 5000 
feet above Mount Baker, in Washington, and thence descends westward 
to the Sound level in the form of a broad and somewhat regular slope. 

As a whole, then, the Cascade range has a broad though greatly 
dissected summit about 75 miles wide, upon which is a remarkably 
straight north-south line of several score volcanic peaks. These lie 
not along the central portion of the range but near the eastern margin, 
so that the greater mass of the range lies west of the geographic sum- 
mit and watershed. From the crowning line of peaks long, broad, 
flat-topped spurs, some of them having almost the magnitude of dis- 
tinct ranges, descend eastward to the Columbia Plateaus and Great 
Basin; that part of the range west of the summit consists of long mas- 
sive mountain spurs (generally with accordant altitudes on north-south 
lines) and intervening deep canyons. The lava flows extending outward 
from the line of the now extinct volcanoes have altered the drainage 
courses greatly by damming the streams, thus causing lakes, marshes, 
and new outlets. These changes have taken place so recently as to 
give the drainage lines many youthful features. 

The eastern margin of the Cascades extends southward from the 
vicinity of Osoyoos lake on the 49th parallel to Ellensberg and thence 
down the west side of the Yakima Valley and across the Columbia 
into Oregon. On this side the slope has marginal flutings which ex- 
tend nearly at right angles to the major uplift some distance into the 
lower Columbia Plateaus on the east and give the margin in places 
an extremely irregular outline.^ 

1 Smith and Willis, The Physiography of the Cascades in Central Washington, Prof. Paper 
U. S. Gaol. Surv. No. 19, 1900, p. 25. 



CASCADE AND SIERRA NEVADA MOUNTAINS 



155 



Long, gentle slopes along the flanks of the ridges descend to the valley floors. The dip of 
the rock and the inclination of the slopes of the ridges agree in direction but differ in amount, 
the dip of the rock commonly exceeding the inclination of the slope. Such a relation of form 
to structure requires the assumption of an erosion period in which was developed a topography 
moderately discordant with respect to structure and later deformed into the attitude in which 
we find it to-day. 

The slopes of the older surface have a remarkably smooth development and are so regularly 
coordinated that the marks of recent dissection are not readily distinguishable in a view along 
the border. There appears to be only a gently inclined surface extending without perceptible 
break from the even-crested ridges to the valley floor. As a matter of fact, narrow gulches 
alternate with the ridges. i 

Deformations of the ancient surface occurred in many places, and all 
show that the uplift of the Cascade lowland to form the Cascade plateau 
or mountains was not a simple broad 
anticlinal uplift or fault block def- 
ormation but a deformation of 
complex character.^ There was at 
least one important halt in the uplift 
during which a mature topography 
was developed in places. One of 
the most important facts relating to 
the broad deformation of the for- 
merly peneplaned surface now up- 
lifted and dissected into the forms 
of the Cascades is the antecedent 
course of the Columbia River. After 
flowing for several hundred miles 
along the eastern front of the Cas- 
cades in Washington this trunk 
stream turns nearly at right angles and strikes boldly across the very heart 
of the Cascades. From a width of 2000 feet at the point where the 
Snake River enters it, the Columbia narrows to from 130 to 200 feet at 
"the Dalles," where it is bordered by high basaltic cliffs.^ The river 
thus bears an antecedent relation to the range, having maintained a 
course outlined upon the Tertiary (Pliocene) peneplain. 

1 Smith and Willis, The Physiography of the Cascades in Central Washington, Prof. Paper 
U. S. Geol. Surv. No. 19, 1900, p. 26. 

2 Idem. 

3 The narrow portion of the channel terminates at the foot of a line of falls and rapids 
called "The Cascades," whence the name of the mountains (see especially George Gibbs, 
Physical Geography of the North-Western Boundary of the United States, Jour. Am. Geog. 
Soc, vol. 3, 1870-71, pp. 144, 147, 148). 




Fig. 34. — Section showing relations of former and 
present forest near Prospect Peak, Cal. 

I. Original soil. 2. Volcanic ashes and 
lapilli. 3. Tree of former forest, killed by 
shower of volcanic ashes. 4. Pit formed by 
decay of old stump. 5. Tree of present forest. 
(Diller, U. S. Geol. Surv.) 



156 FOREST PHYSIOGRAPHY 

Southern Cascades 

The southern end of the Cascades is the Lassen Peak volcanic ridge 
which extends southeast from the Pitt River to the North Fork of the 
Feather River. The ridge is about 25 miles wide and 50 miles long. 
It was built up by eruptions from more than 120 volcanic vents. A few 
of the craters are over a mile in diameter and were centers of enormous 
eruptions. All the prominent peaks of the ridge are volcanic cones. 
The last of the eruptions occurred very recently, a number of them taking 
place probably not more than 200 years ago; some of the trees killed at 
the time are still standing. Large portions of the original pine forest 
were covered with a mantle of volcanic sand or overwhelmed by lava 
during the more recent eruptions. In places the trees of the older 
forest project above the volcanic sand, their bare trunks forming a strik- 
ing contrast to the new green forest developed at a higher level, Fig. 34. 

The western slope of the volcanic ridge is relatively gentle and is 
underlain by volcanic material in the form of lava flows or agglomerate 
tuff. It is dry and sterile, and the larger part is strewn with rough lava 
fragments. The eastern slopes are in general bold. 

The Lassen Peak volcanic ridge is from 5000 to 9000 feet high and 
about 4000 feet above the Great Valley of California on the southwest 
and the Great Basin on the east. Its highest point, Lassen Peak, is 
10,437 feet above the sea. The ridge receives a sufficient rainfall to 
support an open forest of pines. 

Northern Cascades 

Immediately north of the 49th parallel the Cascades terminate 
abruptly and descend to a plateau several thousand feet lower; imme- 
diately south of the 49th parallel the Cascades have their greatest 
development. The distance from Mount Chopaka on the eastern to 
Mount Baker on the western side of the northern Cascades is about 
90 miles. Thus by a pure coincidence the international boundary is also 
a physiographic boundary although it follows a parallel. 

Like the Sierra Nevada Mountains, the Cascades terminate on the 
north in a triple set of subranges, the Okanogan, Hozomeen, and Skagit 
mountains. The Okanogan Mountains extend from Mount Chopaka 
to the valley of the Pasayten River. On the east the Okanogan Moun- 
tains terminate abruptly in a narrow foothill belt. Mount Chopaka 
here rises as a steep wall over 7000 feet high on the border of the Sim- 
ilkameen Valley. Between the Pasayten River and the Skagit River is 
the Hozomeen range; west of the Skagit River are the Skagit Mountains. 



CASCADE AND SIERRA NEVADA MOUNTAINS 



157 



The north-south valleys of the Pasayten and Skagit thus form the divid- 
ing lines between the three subranges of the northern Cascades. We 
shall now briefly examine the detailed characteristics of each of these 
ranges. 

The Okanogan Mountains consist of a great batholith of granitic 
rocks and are perhaps the most important igneous member of the Cas- 




Fig- 35- — Cathedral Peak, Okanogan Mountains, Washington, showing glaciated summit of the matter- 
horn type. Nearly vertical jointing in granite rock has assisted glacial erosion in producing rugged 
forms. (Smith & Calkins, U. S. Geol. Surv.) 

cades. The Skagit and Hozomeen ranges are composed chiefly of sedi- 
mentary rock, with a large amount of conglomerate, slate, and schist, 
the latter having structures with a north-south trend. ^ The Okanogan 
Mountains have a number of high peaks such as Chopaka, Cathedral, 
Remmel, and Bighorn, with a nearly uniform elevation of 8000 to 
8500 feet. Almost all the mountain peaks are above the 7000-foot 
level. The highest peaks are extremely rugged, and are bordered by 
deep glaciated valleys. Glaciers still persist on the north sides of a few 
peaks, but they are of small size. The evidences of former more exten- 
sive glaciation are particularly well shown in the deeply carved north- 
ern aspects of spurs and ridges where steep-sided cirques and gulches 

1 Smith and Calkins, A Geological Reconnaissance Across the Cascade Range near the 
49th Parallel, Bull. U. S. Geol. Surv. No. 235, 1904, p. 84. 



158 FOREST PHYSIOGRAPHY 

abound. The southern slopes are more regular and without glacial 
modification. Small lakes with bordering snow banks occupy almost 
all the glacial amphitheaters that are tributary to the Similkameen. 

Hozomeen range includes the central and main crest of the northern 
Cascades. Its western flank is scored by a number of remarkably 
narrow canyons, among which is the Skagit, whose mouth is so narrow 
as barely to permit the passage of the stream. The divide of the range 
has an elevation of 7000 to 8000 feet, and about ten miles south of the 
49th parallel consists of sharp peaks with rugged outlines due to the 
irregular, coarse, and resistant conglomerate of which they are com- 
posed and the deep dissection of the range of which they form a part. 
Numerous glaciers occur and glacial cirques have been cut back into 
the main mass of the mountain to such an extent that the peaks are 
largely of the pyramidal or matterhorn type. North of the boundary 
the topography of this subrange becomes much less bold. 

Skagit Mountains form the western subrange of the Cascades and 
include the wildest and most rugged country of the entire section. 
High peaks with precipitous sides abound and the scenery is extraordi- 
narily picturesque. The mountain slopes are so steep that much of the 
country is practically inaccessible and unknown even to prospectors. 
Sharp, glaciated, pyramidal peaks are characteristic of the range about 
the headwaters of the Nooksak and Chilli whack rivers. Some of the 
higher peaks are still flanked by glaciers, the feeble descendants of the 
large Pleistocene glaciers that are responsible for the development of 
amphitheaters with extremely steep walls and for the pyramidal peaks 
which occur throughout the range. The western portion of the Skagit 
Mountains consists of broader ridges, essentially flat-crested, smooth, 
grass-covered, and separated by broad steep- walled canyons. The 
western border of the northern Cascades is marked by an abrupt 
descent to the gravel- covered plain that extends west to the coast. ^ 

The flat-topped ridges of the Skagit range west of the Mount Baker 
district have a somewhat uniform elevation of 5000 to 6000 feet and a 
gentle westerly inclination. The flat tops are interpreted as the rem- 
nants of a preexisting topography which once occurred in the form of 
a fairly perfect lowland with few residuals rising above the general 
surface. Later uplift supplied an opportunity for vigorous dissection. 
Where the uplift was from 5000 to 6000 feet remnants of the old sur- 
face remain on the divides. Where the uplift was 7000 feet and more 
no traces of the old lowland persist, the peaks are acute pinnacles, the 

1 Smith and Calkins, A Geological Reconnaissance Across the Cascade Range near the 
49th Parallel, Bull. U. S. Geol. Surv. No. 235, 1904, pp. 13-17. 



CASCADE AND SIERRA NEVADA MOUNTAINS 



159 



divides mere knife-edges. In the Okanogan Mountains the peaks at 
8000 feet are approximately uniform in altitude and merely suggest an 
older topography. At the time of uplift of the northern Cascades from 
base level there appears to have been not a single broad up warp; the 
three subranges composing the northern Cascades represent distinct 
upwarps separated from each other by downwarps which have deter- 
mined the positions of Pasayten and Skagit valleys.^ 

The abrupt termination of the Cascade Mountains at the inter- 
national boundary line has been shown to be due to a difference in 




^^-i^^. - ^.^ V,. ^^:a^^. 



Fig. 36. — Plateau of the Cascades representing uplifted and dissected lowland surface. Western por- 
tion of Skagit Mountains, Mount Baker in left background. Looking west from Bear Mountain. 
(Smith and Calkins, U. S. Geol Surv.) 

degree of uplift between the Cascade country and the Interior Plateau 
of British Columbia since the last erosion cycle common to both moun- 
tains and plateau. The earlier structures so far as known appear to 
extend from one province to the other, denoting a common geologic 
history down to the Eocene.^ In the latter part of the Pliocene, uplift 
of the base-leveled surface common to both took place, but the uplift was 
differential and amounted to about 4000 feet in the Interior Plateau and 
about 8000 feet in the Cascades. The uplift of 8000 feet was, however, 
not uniform throughout the Cascades; it w^as an uplift in the form of 
upwarps and downwarps, the upwarps being represented to-day by the 
three parallel ranges constituting the northern end of the Cascades, and 

1 Smith and Calkins, A Geological Reconnaissance Across the Cascade Range near the 
49th Parallel, Bull. U. S. Geol. Surv. No. 235, 1904, p. 89. 

2 G. M. Dawson, Trans. Royal Soc. Canada, sec. 4, 1S90, p. 16. 



l6o FOREST PHYSIOGRAPHY 

the downwarps by the intervening valleys. During the upwarping cer- 
tain streams persisted across the structures upraised in their paths, such 
as the Skagit across the Skagit Range, the Columbia across the Cascades, 
and the Frazer across the Interior Plateau. All these streams are there- 
fore antecedent in portions of their courses. The differences between 
the Cascade ranges on the one hand and the Interior Plateau and 
Columbia Plateaus on the other are therefore due fundamentally to 
differences of elevation and degree of dissection conditioned by uplift. 
The eastern margin of the peneplain of the Cascades descends gradually 
to the plateaus of the Columbia apparently without a break; a similar 
but more sudden descent marks the northern end of the Cascades 
where they descend to the level of the Interior Plateau of British 
Columbia. 

The rather general occurrence of the Columbia River lavas over a 
large part of the northern and central Cascades is accounted for by the 
fact that the extrusion of the lavas took place mainly at a time when 
the low relief of the land allowed their widespread distribution. These 
great basaltic inundations are to be distinguished from the much 
later volcanic outpourings that formed the cones now surmounting the 
Cascades. Mount Baker, for example, like most of the highest peaks 
of the Cascades, is an extinct volcano, built up of andesitic lavas of 
rather recent age poured out upon a topography as rough as the present ; 
and the main drainage feature of the region, the Nooksak, was, at the 
time of the eruption of the lavas, practically at the present level and 
in the present position. "^ 

All the higher peaks of the Cascades, as well as the lower country, 
were glaciated during the Pleistocene period, the lower limit of glaciation 
ranging from sea level in the Sound Valley to heights of several thousand 
feet, its position depending on exposure, latitude, etc. The evidences 
of past glaciation are of the familiar sort and consist of terminal and 
lateral moraines, glacially modified valleys, and aggraded stream courses 
at lower altitudes. Probably the most important topographic and drain- 
age effects in the Cascades occurred in Washington in the vicinity of 
Lake Chelan. 

" Lake Chelan is a splendid body of water 65 miles long whose southeastern end lies open 
to the sky between the grass-grown hills of the outer Columbia Valley, while its northwestern 
end lies in shadow between precipitous mountains in the heart of the Cascade range. There 
are sandy shallows near its outlet, but beneath the cliffs of its upper course the water is pro- 
foundly deep." 2 

1 Smith and Calkins, A Geological Recormaissance Across the Cascade Range near the 
49th Parallel, Bull. U. S. Geol. Surv. No. 235, 1904, p. 35. 

2 Smith and Willis, The Physiography of the Cascades in Central Washington, Prof. Paper 
U. S. Geol. Surv. No. 19, 1900, p. 58. 



CASCADE AND SIERRA NEVADA MOUNTAINS 



l6l 



The lake lies in the canyon of the Stehekin-Chelan River and 32 miles 
of its length lies within the Cascade Mountains. The depth of the lake 
varies from 1000 to 1400 feet, and as the water's surface is but 1079 feet 
above the sea, the bottom of the lake is at one place 300 feet below sea 
level. The water is partially retained at its present level by a dam of 
sand and gravel. It appears that the valley now partly filled by Lake 
Chelan was occupied by a great mountain glacier that deepened and 
widened the preglacial valley and steepened the valley walls, giving 
them their present precipitous character. 

The glacial features of the northern Cascades are markedly asym- 
metric. For example, the U-shaped canyons that drain eastward to 




Fig- 37- — Relief map of Mount Hood, Oregon, showing the eroded condition of the 
volcano and the extent of its glacier systems. (U. S. Geol. Surv.) 

the Pasayten have northern walls of great simplicity and southern or 
shady walls carved into niches or hanging cirques of glacial origin. 
The average or prevailing aspect of the glacial cirques of the entire region 
is about due northeast, a feature probably due to the preglacial topog- 
raphy, lesser insolation on that aspect, and a certain excess of snow 
accumulated by drifting across the divide. The more favorable easterly 
aspect is well illustrated by the glacial erosion of the Hozomeen range, 
the glaciers flowing eastward having eaten back into the heart of the 
range much more than their rivals in the western valleys. So marked 
is this feature that many of the higher peaks have a degree of asymmetry 
suggesting a breaking wave.'^ 

1 Smith and Calkins, A Geological Reconnaissance Across the Cascade Range near the 
49th Parallel, Bull. U. S. Geol. Surv. No. 235, 1904, pp. 90-gi. 



l62 FOREST PHYSIOGRAPHY 

Glacier systems are still prominent features of the higher peaks. 
Mount Rainier, Mount Hood, and others are flanked by short glaciers 
above the 8000-foot level. Fig. 37. The snow and ice fields not only 
enhance the beauty of these splendid volcanoes but also serve to steady 
the discharge of the rivers which they feed. 

Soil, Climate, and Forests 

The almost endless variety of rocks which form the Cascades causes 
the valley soils to be formed of a great variety of mineral fragments. 
The valley soils do not therefore reflect the nature of the nearest 
rock exposures to an important degree. In the higher valleys and 
basins which lie parallel to the trends of the structures the soil retains 
to some degree the mineral characteristics of the rock (chiefly granite) 
from which it was derived. So far as surveys have been made the 
granitic rocks appear to be sandier and drier because of the mineral 
composition of the parent rock. They are therefore covered with a 
shrubby, grassy vegetation ; the schist and slate rocks furnish a finer soil 
with a larger proportion of clay, and appear to be heavily wooded. 
At the higher elevations, however, the one exhibits rounded forms, the 
other is developed into a sharply serrate topography imfavorable to 
heavy tree growth. Toward the valley heads the land waste is coarse 
and bowldery; down valley a gradation in size is effected through trans- 
portation and deposition by water; the soils of the lower valleys are 
fine. 

The total precipitation of the central Cascades varies from 60 to 100 
inches a year. Three-fourths of it occurs in the winter season from 
November to May. In the higher portions of the range the snowfall 
is heavy, varying from 4 to 10 feet in depth. In these situations it re- 
mains throughout the winter, and, in restricted summit areas, through- 
out the year. On the highest peaks precipitation is alm.ost wholly in 
the form of snow and well-defined glaciers, from a fraction of a mile to 
several miles in length, flank Mount Hood, Mount Rainier, and other 
peaks. The more important streams as a rule have their headwater 
sources in fields of perpetual ice and snow. Snowstorms in the lower and 
middle portions of the Cascades (Mount Hood region) are usually fol- 
lowed by rains and warm chinook winds which dissolve the snows and 
cause extremely heavy freshets in all the streams.^ 

The forests of Washington cover the state as a thick mantle from 
high elevations on the Cascade range westward to the Pacific. In this 

1 H. D. Langville and others, Forest Conditions in the Cascade Range Forest Reserve, 
Oregon, Prof. Paper U. S. Geol. Surv. No. 9, 1903, pp. 29, 30, 



CASCADE AND SIERRA NEVADA MOUNTAINS 



163 



great region the only mountains that reach above timber line are the 
Olympics in the Coast Range System and a limited number of peaks in 
the Cascades. The forests are the densest, heaviest, and most continuous 
in the United States except for the redwood area in northwestern Cali- 
fornia, and are marked by a dense and tangled undergrowth. The largest 
trees are from 12 to 15 feet in diameter and 250 feet in height. Red or 




miles 80 Sea Level 175 250 310 390 

Fig. 38. — Topographic profile in relation to rainfall in the Coast Ranges and the Cascades of Oregon. 

yellow fir, in the zone of heaviest rainfall and where there is at least 
a moderate soil cover, constitutes the larger part of the forest, with an 
intermingling of spruce, hemlock, and cedar.^ 

West of the Cascade range the country is occupied mainly by four 
species, red fir, cedar, hemlock, and spruce. The percentages of com- 
position arranged in the same order are as follows: 64, 16, 14, and 6, with 
the proportions of cedar and spruce increasing toward the coast. At 
the highest elevations the far disappears and hemlock and cedar come in. 
East of the Cascades the climate becomes rapidly drier and the timber 
consists almost entirely of lodgepole and yellow pine.^ 

In Oregon the timber consists of about the same species as in Wash- 
ington, with the addition in the southwestern part of the state of sugar 
pine, noble fir, and yellow pine. The red fir constitutes by far the larger 
part of all the timber in the state. Cedar, hemlock, and spruce are 
comparatively unimportant, except along the coast. The fir occupies 
the entire timbered portion of the western slope of the Cascades, the 

1 Henry Gannett, igth Ann. Kept. U. S. Gaol. Surv., 1897-98, p. 26. 
• Idem, p. 27. 



164 



FOREST PHYSIOGRAPHY 



eastern slope of the Coast Ranges, and the depression between these 
mountains where it forms more than three-fourths of the forest. The 
cedar occurs mainly at mid-altitudes upon the Coast Ranges and the 
Cascades but forms a small proportion of the forest. Hemlock occurs 
notably upon the western slope of the Cascade range at mid-altitudes. 
East of the Cascade range in Oregon the forests are largely of yellow 
pine. Sugar pine extends over the entire breadth of the Cascades and 
from California northward to the Columbia and westward to the coast. 




Fig. 39. — Altitudinal range and development of timber-tree species in the central portion of the Cascade 
Mountains. (U. S. Geol. Surv.) 



On account of the exceptional height, breadth, and topographic 
boldness of the northern Cascades their climatic and forest characters 
deserve special discussion. The northern end of the Cascades is a 
region of short summers, comparatively free from rains. The winter 
snowfall, however, is extremely heavy. Besides its important relation 
to irrigation through its tendency to equalize stream flow, the heavy 
snowfall is of ecologic importance, for it determines the distribution of 
certain definite plant communities, influences the forms of plants as 
along the cold timber line where dwarfed or gnarled forms occur, and 
prevents excessive temperatures and too rapid transpiration during 
winter storms when the roots are incapable of absorbing water. In the 



CASCADE AND SIERRA NEVADA MOUNTAINS 165 

Okanogan Mountains the snow does not disappear until the middle of 
July, and several miles south of the 49th parallel deep snow remains 
throughout the summer and snow squalls occur even in July and August. 
Similar climatic conditions occur in the eastern part of the Hozomeeh 
range, but the western slope of this range has a much greater annual 
precipitation. The forests become extensive, large trees with dense 
underbrush cover the valley bottoms and extend well up the slopes, 
and grass is not plentiful except on a few ridges. Banks of snow persist 
throughout the year and glaciers occur on all the higher peaks. In 
the Skagit Mountains the summer is very short and July and August are 
the only months in which snow does not fall in considerable amounts. 
At no time in the year are the passes in the Skagit Mountains free from 
snow. 

The climatic contrasts between the east and west slopes of the Cascades are well shown by 
the conditions of the old vistas cut on portions of the boundary line. In the Pasayten Valley 
the cuttings can be found easily, the stumps and logs are sound, and camp stools remain as they 
were left forty years ago. On the western slopes and in the Skagit Valley the old stumps are so 
decayed as to be barely recognizable, and the vista is here occupied by trees 75 feet high and 
14 inches in diameter, which have grown up in the old cuttings in that short time.' 

On the western slopes of the northern Cascades there is a heavy pre- 
cipitation which supports a dense forest growth. Timber line is at 6000 
feet; above this elevation trees occur only in groves or singly and most 
of the mountain summits are treeless. Grasses, sedges, and heather 
are the common growths above the forest. The best forest growth is 
below 4000 feet Above that elevation the trees are apt to be shorter and 
more branched, and the trunks twisted or otherwise defective. Some of 
the basins at rather low altitudes are without forests on account of the 
accumulated snows which melt out too late in the spring to favor any- 
thing but a growth of grass. The red fir belt is the lowest of the 
three forest belts recognized here, and has associated with it the Sitka 
spruce, the silver fir, the hemlock, and other species. The main slopes 
of the mountain spurs are covered with hemlock and white fir, which 
constitute the second forest belt. In the third or alpine belt on the 
summits of the principal spurs and on the divides the growth is sparse 
or absent. The principal trees of the alpine zone are the mountain 
hemlock, alpine fir, and Engelmann spruce.^ 

The heavy rainfall of the western slopes slightly overlaps the upper 
part of the eastern slope of the Cascades and is accompanied by trees 

» Smith and Calkins, A Geological Reconnaissance across the Cascade Range near the 49th 
Parallel, Bull. U. S. Geol. Surv. No. 235, 1904, p. 18. 

2 H. B. Ayres, Washington Forest Reserve, 19th Ann. Rept. U. S. Geol. Surv., pt. 5, 1897-98, 
pp. 283-293. 



1 66 FOREST PHYSIOGRAPHY 

characteristic of the western zone. These extend eastward over the 
geographical summit of the range, a feature less marked on the higher 
saddles, ridges, and peaks and very strongly marked in the low passes. 

Sierra Nevada Mountains 

The Sierra Nevada Mountains on the eastern border of California 
are a bold, continuous range about 75 miles in width. They have many 
well-defined peaks; the larger number occur in a line west of Lake 
Tahoe, Owen's Lake, etc., and constitute what is generally known as the 
High Sierra, the crest line of the Sierra Nevada Mountains over 11,000 
feet in height. By reason of the dominating character of the Sierra 
Nevada and its high degree of effectiveness in barring the rains and 
snows of the westerly winds, it has an abundant water supply and is 
well clothed with forests of pine, fir, hemlock, etc. ; in both these respects 
it is strikingly different from the minor north-south ranges on the east 
that comprise so large a portion of the Great Basin, and from the nearly 
treeless central valley of California on the west. 

The Sierra Nevada is a notable example of a mountain range of great geologic complexity 
whose general physiography is of a rather simple type. In order that this may be realized a 
few geologic details may be given. It is probable that the Sierra Nevada rock formations 
range in age from Archeean or Algonquin to Recent. ^ The rocks have been profoundly 
affected by crustal compression accompanied by close faulting and schistosity, in many places 
carried to the point where the original nature of the sediments has been completely altered. 
These statements are sufficient to show that a complete geologic study of the mountains would 
include a wide range of facts related to almost every department of geologic science. Com- 
pression and folding occurred at the end of the Paleozoic, as well as a certain amount of igne- 
ous intrusion, and later the mountains were greatly eroded. At the close of the Jurassic the 
Sierra Nevada region was again compressed and folded as well as uplifted into the form of a 
prominent mountain range. Great batholithic intrusions also took place at this time. In con- 
nection with these intrusions the sedimentary rocks were largely metamorphosed and rendered 
schistose and platy.2 These two facts, as we shall see in succeeding pages, are of first impor- 
tance in the interpretation of the canyon forms associated with the Yosemite, Merced, Tuolumne, 
and other mountain streams. 

In spite of the great geologic complexity of the Sierra Nevada 
Mountains their broader physiographic features are somewhat simple. 
Whatever the original relief, now lost, may have been, and however 
complex the structural changes that have taken place, these are on 
the whole of lesser importance geographically than peneplanation which 
brought about the existence of a topography of little relief. The high- 
est mountains were reduced to residual mountains, the valleys were 
broadened out to great width, and the streams flowed in courses of 
slight gradient. As in so many other instances of peneplanation, the 

1 H. W. Turner, 14th Ann. Kept. U. S. Geol. Surv., pt. 2, p. 445. 

2 J. S. Diller, Bull. U. S. Geol. Surv. No. 353, 1909, pp. 8-9. 



CASCADE AND SIERRA NEVADA MOUNTAINS 1 67 

structure of the country was practically unexpressed in its topography: 
high and low masses, hard and soft rocks, were as a rule brought down 
to a common topographic expression. Upon the floors of the ancient 
valleys that but slightly diversified the relief of the ancient peneplain 
(completed in the Miocene) auriferous gravels were deposited, and among 
the finer sediments are fossil leaves of the fig, oak, and other plants 
indicative of a low coastal country somewhat like Florida. The uplift 
of the peneplain was accompanied by volcanic activity. From volcanic 
vents near the low crests streams of lava issued and followed the water- 
courses, covering the auriferous valley gravels and displacing many of the 
streams.^ 

The Sierra Nevada Mountains, as we know them to-day, are among 
the major relief features of the continent, and the contrast between 
their former peneplaned and their present mountainous condition can be 
understood from the fact that block faulting on a large scale has taken 
place, resulting in both the bodily uplift and the tilting of a large crust 
block. The eastern face of the Sierra Nevada over a distance of several 
hundred miles is exceedingly steep and forms a fault scarp which is to be 
compared in steepness and continuity only with the eastern face of the 
Lewis Mountains in western Montana (p. 307). Among the facts sup- 
porting the hypothesis of faulting are the stream gravels on the very 
summits of the mountains above the steep eastern scarp where in places 
they are displaced through 3000 feet of vertical distance- 
Evidence of recent faulting has been found along the eastern base of the mountains, near 
Genoa, where alluvial deposits (Pleistocene) have been displaced some 40 feet; it has also been 
found that the Carson River on emerging from the mountains increases its grade abruptly 
toward the east, suggesting recent dislocation of its valley. It is concluded that the first dis- 
location along the eastern face of the Sierra Nevada Mountains took place at the close of the 
Cretaceous and that it has continued down to the present day, thus making the faulting com- 
plex. A number of more or less parallel faults have been identified within a belt 25 miles wide.^ 

Along most of the range the rocks of the Sierra Nevada scarp do not 
end finally, but occur in the ranges to eastward, a feature explained by 
a system of compound faults parallel with the eastern front of the major 
range. It is in the depressions between the main Sierra block and the 
subsidiary blocks that the chief lakes of the region occur, as Owen's Lake, 
Mono Lake, Tahoe Lake.^ The Carson topographic sheet well represents 

I J. S. Diller, Bull. U. S. Geol. Surv. No. 353, 1909, p. 9- 

- J. S. Diller, 14th Ann. Rept. U. S. Geol. Surv., pt. 2, p. 432; H. W. Turner, 14th .Ann. 
Rept. U. S. Geol. Surv., pt. 2, p. 442; I. C. Russell, 8th knn. Rept. U. S. Geol. Surv., pt. i, 
p. 322. 

^ Auriferous Gravels of the Sierra Nevada, Jour. Geol., vol. 4, quoted by Spurr in Descrip- 
tive Geology of Nevada South of the 40th Parallel, and Adjacent Portions of California, 
Second Edition, Bull. U. S. Geol. Surv. No. 208, p. 222. 

* See Contour Map of the United States, scale in miles to the inch, U. S. Geol. Surv. 



1 68 FOREST PHYSIOGRAPHY 

this feature so common in the Great Basin region and marked out on 
very strong lines along the eastern border of the Sierra Nevada. The 
main intermont valley is broken by secondary blocks into a series of 
subordinate valleys. The secondary blocks are generally discontinuous 
longitudinally and the greater number of them are roughly parallel to 
the primary fault plane. The eastern slope of the Sierra Nevada Moun- 
tains thus exhibits a multiple scarp. 

As an illustration of a depression due to deformation of the crust 
block type may be cited Owen's Valley, a V-shaped depression between 
the Sierra Nevada and the White Mountain blocks. This conclusion is 
based upon the fact that faulting and associated phenomena have been 
observed in many places along the eastern margin of the Sierra Nevada 
and also on the eastern margin of the White Mountains. Furthermore, 
hot springs occur in the marginal zone from the midst of Owen's Valley 
to Mono Lake, and a mud geyser is known at Casa Diablo, two features 
whose occurrence is commonly associated with faulting. The sharp 
truncation along the eastern border of the mountains of the inclined 
peneplain of the western slope of the Sierra Nevada, a feature w^ell 
developed on the steep eastern face of the White Mountains in sharp 
contrast to the gentle western slope, points to the same conclusion. 
Finally, faulting and crustal movements of considerable magnitude and 
accompanied by earthquake shocks have taken place in Owen's Valley 
in historic time.^ 

In contrast to the steep eastern front of the Sierras is the gentle 
westward slope that descends from 9000 feet on the east to the 1000-foot 
level on the west at the border of the central valley of California. From 
any commanding view between the crest of the range and the valley of 
California one looks out upon a plateau whose general accordance of 
summit levels is striking and significant. This was once a broad plain 
near sea level, now uplifted to a great height.^ Though peneplanation 
may be safely inferred from the discordance between the plane of the 
sublevel hilltops and the structure, the region is nevertheless deeply dis- 
sected by the rejuvenated streams. Canyons have been formed of such 

1 W. T. Lee, Geology and Water Resources of Owen's Valley, California, Water-Supply 
Paper U. S. Gaol. Surv. No. i8i, igo6, p. 25. 

2 The peneplain of the western slope of the Sierra Nevada was first recognized by Gilbert 
(G. K. Gilbert, Science, vol. i, 1883, pp. 194-195). Diller showed that the planation was 
probably accomplished during Miocene time (J. S. Diller, Tertiary Revolution in Topography 
of the Pacific Coast, 14th Ann. Rept. U. S. Geol. Surv., pt. 2, 1894, pp. 404-411). He 
also found that gravel deposited upon this peneplain had been elevated, faulted, and tilted, 
the degree of vertical displacement along the eastern face of the range being 3000 feet at the 
northern end. 



CASCADE AND SIERRA NEVADA MOUNTAINS 



169 




Fig. 40. — Typical portion of Yosemite Valley, showing cliffed margins, waterfalls, flat floor, and mean- 
dering stream. Partly stream eroded, partly ice eroded canyon whose details of cliff structure are 
due to geologic structure. (Matthes, Yosemite Valley Map, U. S. Geol. Surv.) 



lyo FOREST PHYSIOGRAPHY 

profound depth and steepness as to constitute the chief scenic feature of 
the range outside the snow-capped High Sierra. 

The main streams such as the Merced, Tuolumne, Feather, and Hetch- 
Hetchy flow in canyons from a half mile to a mile deep. The encan- 
yoned portions of the streams are but fractions of the total lengths of the 
streams, since the canyons do not appear either at the headwaters or 
in the foothill belt. They are limited to the intermediate levels where 
the alpine glaciers once occupying the largest valleys produced their 
most important topographic effects. All the canyons have exceedingly 
steep walls over which tributary streams form waterfalls of celebrated 
beauty. Rarely does flat land of any extent occur on the canyon floors, 
though this feature is well developed in the Yosemite and the Hetch- 
Hetchy where open grassy glades diversify the forest cover and possess a 
charm possessed in equal degree by few regions in the world. The canyon 
of the Yosemite, the most celebrated in the region, has long been regarded 
as due wholly to glacial erosion, but recently it has been more safely 
determined to be not solely a normal product of ordinary stream or 
ice erosion but equally a function of the structure of the country 
rock. The granites of the Yosemite region consist of many huge mono- 
lithic masses embedded in a matrix of more or less strongly fissured 
rock. There is in consequence extreme inequality of resistance to dis- 
section and the landscape reflects very faithfully each structural charac- 
ter of the material from which it was carved. The dominating heights, 
such as Half Dome, consist invariably of resistant monoliths; the can- 
yons and gorges are due to the erosion of zones of nonresistant fissile 
rocks; the courses of the rivers and lake basins in the valley floors 
and the scarp-like rock walls were in all cases evolved in obedience 
to local structural conditions. The trend and profile of each cliff are an 
expression of its associated structure.^ 

The Sierra Nevada block south of latitude 38° 30' is displaced along 
its eastern face, chiefly along a single fault line, and the range is here 
much higher than to the north, and bears upon its summit a number 
of exceptionally high peaks, among them Mount Whitney, the highest 
mountain in the United States (14,800 feet). 

This portion of the mountains, the High Sierra, should not be con- 
sidered as a part of the ancient peneplain, since it stands several 
thousand feet above the general summit level of the Sierra Nevada. It 
is an unreduced or residual portion of the region. The main range of 
the Sierra is thus a belt of extremely high relief about 25 miles wide, 

1 F. E. Matthes, The CliS Sculpture of the Yosemite Valley, Paper before the Geol. See. 
Am., Dec, igog, p. 4. 



CASCADE AND SIERRA NEVADA MOUNTAINS 171 

with numerous sharp spurs and ridges among which there are few tracts 
of valley land. Level tracts of limited extent, however, occur at the 
heads of most of the larger streams, and a few large streams have head- 
waters draining big valleys or lakes. This is true of the northern and 
lower Sierra Nevada especially. Thus the Middle Fork of the Feather 
River issues from a large level tract known as Sierra Valley, about 
60,000 acres in extent, and Truckee River flows out of Lake Tahoe, 
190 square miles in extent. Carson Valley and Little Valley west of 
Washoe Lake are further illustrations. The smaller streams drain 
small glades, ponds, or lakelets or rise directly from steep mountain 
flanks.^ 

In a broad view of the Sierra Nevada, five categories of form are thus 
distinguishable: (i) a summit zone of residual elevations, including the 
High Sierra and many lesser elevations, (2) a plateau zone representing 
an uplifted, tilted, and partly dissected peneplain, (3) a fault zone on 
the eastern border of the range, including steep, recently formed, and 
but little dissected fault scarps which are in almost startling contrast 
to the flat ridge tops that represent peneplain remnants, (4) a narrow, 
structural valley zone on the east in which the valleys represent fault 
depressions, (5) a broader valley zone on the west, in which the val- 
leys are canyons of erosional origin whose architectural details alone 
are responses to structure.^ 

The uphft of the Sierra Nevada block rearranged the drainage of the 
region in many localities. In a general view of the drainage promi- 
nent features are the short and steep streams that descend the eastern 
scarp of the Sierra Nevada block and the generally direct courses of the 
streams draining the gentler western slope. It is noteworthy that 
the westward-flowing streams have a certain axial directness down the 
incline of the block, courses which appear to have been gained during or 
as a result of the block deformation, for their inharmonious relations to 
the structure indicate that they are formed upon a peneplaned surface 
deeply covered with land waste and at a time when hard and soft rocks 
did not show any important topographic differences. Several streams 
appear to have maintained their courses across the rising Sierra Nevada 
block in spite of the uplift. The forks of the Feather River persisted in 
their courses and cut deep canyons directly across the rising crests of some 
of the individual blocks of the range. The effect of the deformation 

1 J. B. Leiberg, Forest Conditions in the Northern Sierra Nevada, California, Prof. Paper 
U. S. Geol. Surv. No. 8, 1902, p. 17. 

2 For a detailed description of the first four zones as developed in the Carson Lake district 
northeast of Lake Tahoe see J. A. Reid, The Geomorphogeny of the Sierra Nevada Northeast 
of Lake Tahoe, Bull. Dept. Geol., Univ. Cal. Pub., vol. 6, 191 1, p. 108. 



172 FOREST PHYSIOGRAPHY 

was to bring the ancient bed of the Jura River to unequal elevations 
above the present bed, giving the ancient bed an abnormal profile, so 
that the old and now lithified river gravels arch over a secondary block 
of the Sierra. 

The northern end of the Sierra Nevada is more complex than other 
portions of the range. Beyond Lake Tahoe are three main crests, 
Clermont Hill Ridge, Grizzly Mountains, and Diamond Mountain, and 
each crest has a valley at its northeastern base. Each crest represents 
the edge of a tilted crust block whose northeastern face is a fault scarp 
and whose southwestern descent is a dissected remnant of a former 
peneplain. The western crest (Clermont) is continuous with the main 
crest of the range north of Lake Tahoe. The Diamond Mountain block 
of the northern Sierra Nevada has a long gentle slope towards the south- 
west, which gives that side the appearance of a plateau. Toward the 
northeast the mountain presents an escarpment over 200 feet high in a 
short steep slope to Honey Lake, Fig. 28. This escarpment is remark- 
ably regular, with few prominent spurs and reentrants and no important 
stream features which point to a recent origin through faulting. The 
upper courses of the westward-flowing streams are in broad shallow 
valleys developed upon the regional peneplain before uplift and defor- 
mation took place, but as they continue to the southwest their valleys 
become progressively deeper until they have true canyon profiles. All 
of them open into broad alluvial valleys at the foot of the mountain 
slope. Lights Canyon, Cooks Canyon, and the canyons of Indian and 
Squaw creeks are illustrations. The Grizzly Mountain crust block 
repeats the essential features of the Diamond Mountain block except that 
its crest line is less regular; a broad gap has been developed across the 
range and no definite traces of an inclined peneplain may be found upon 
the southwestern slope of the mountain.^ 

SOILS, PRECIPITATION, AND FOREST BELTS 

The soils of the western forested slopes of the Sierra Nevada are 
chiefly residual and have been derived from the weathering of granitic 
rocks, diabase, amphibolites, slates, serpentine, and volcanic material. 
They are prevailingly of light-red to deep-red color, and generally of 
somewhat compact structure. The soils are sometimes separated from 
the underlying parent rock by a thin stratum of adobe-like material. 
They are frequently very shallow and marked by abundant rock out- 
crops, bowlders, and rough, rocky areas. 

1 J. S. Diller, Geology of the Taylorsville Region, California, Bull. U. S. Geol. Surv. No, 353, 
1909, pp. 9-12. 



CASCADE AND SIERRA NEVADA MOUNTAINS 



173 



The slopes of the canyons are generally rocky and almost denuded of 
soil, but deep residual soils are found along the summits of the ridges 
below 4000 feet. Deep-red soils are as a rule found on the andesite, 
gabbro, and diabase-porphyry rocks, while the sedimentary rock is usually 
covered with a poor shallow soil.'^ 

The foothill soils are almost entirely residual and vary in character 
with the nature of the underlying rock. The poorest soil, light colored 
and shallow, is found upon slate. A deeper and warmer soil is found 
upon granite, and the best soil of all — the one richest in plant food — 
is the so-called "red soil," derived principally from the disintegration 
of diabase and amphibolite.^ 

Above 5500 feet on the north and 6500 feet on the south the Sierra 
Nevada has been glaciated and abounds in rocky slopes, tracts of bare 
rock from which the soil has been swept. The present glaciers of the 
High Sierra are very small and occupy only the headwater amphitheaters 

SIERRA NEVADA 

Sl.lS^in. ^ 

n- ^ GREAT BASIN 5 

017^,0! I 



PACIFIC 
OCEAN 



450' 



g SACRAMENTO VALLEY 

§ 19.78 in. •; 



/'/JJJJJ/ r777^ 



>^^^^fff/>j^^^^^^rT. 





Sea Level 25 miles 50 75 100 125 150 175 200 225 260 

Fig. 41. — Relation of topography to rainfall, Sierra Nevada Mountains. 

formed by the larger ancestral glaciers. The extensive glaciers and snow 
fields of the past formed a large part of the existing soil; the present 
glaciers are above tree line, occupy but an insignificant fraction of the 
total surface, and have no important relation to soils or forests. 

The annual precipitation over the Sierra Nevada, Fig. 41, ranges 
from 40 inches at elevations of about 3000 feet to a maximum of 70 
inches at 7000 feet, with less precipitation on the eastern slopes than at 
corresponding elevations on the western slopes.^ The winter snowfall 
at elevations above 4500 to 5000 feet is as a rule heavy, the largest banks 
in the deepest woods persisting until late summer. In the valleys and 
foothills below 1500 feet snow seldom occurs and lasts for only a few 
hours. 

On the western slope of the Sierra Nevada three well-defined zones 
of vegetation may be distinguished: (i) the well-watered, heavily for- 

1 W. Lindgren, Colfax Folio U. S. Geol. Surv. No. 66, igoo, p. lo. 

2 W. Lindgren, Sacramento Folio U. S. Geol. Surv. No. 5, 1894, P- 3- 

3 W. Lindgren, Pyramid Peak Folio U. S. Geol. Surv. No. 31, i8g6, p. i. 



174 FOREST PHYSIOGRAPHY 

ested zone between 3000 and 6000 feet, known as the "timber belt," 
(2) the drier transition belt of thin forest below 3000 feet, and (3) the 
nearly treeless rolling grassy hills which occur between the floor of the 
Great Valley and the slope of the Sierra up to 1500 feet. 

The timber belt contains magnificent forests among which the coni- 
fers predominate both in size and number. They include the yellow 
pine, the sugar pine, and the famous "big trees." The last-named grow 
in quiet hollows protected from the winter storms by the bordering 
ridges and surrounding forests of pines. All the larger conifers likewise 
flourish best in sheltered areas, though they are also found in diminished 
numbers on the ridges. Undergrowth is usually lacking except near 
springs or small streams, and this condition together with the open 
stand of the trees gives the forests a pleasant, park-like character. Within 
the timber belt are also found the spruce, fir, tamarack pine, and sih'er 
fir, the last-named generally clinging to the ridges and higher slopes, 
while the tamarack associated with willows and poplars is found in the 
low, marshy places. In the upper glaciated portion of the timber belt 
the rock has been swept bare of soil and the trees grow under hard con- 
ditions, their roots penetrating soil that fills cracks and joints in the 
granite. 

The higher elevations from 6000 to gooo feet have been denuded of 
their soil by glacial action and are characterized by various species of firs, 
spruce, and tamarack; the silver fir, for example, grows chiefly above 
8000 feet. All the timber of the higher belt is sparse and of poorer 
quality than that found on the lower elevations. The highest slopes are 
rocky and inaccessible and without vegetation. 

The ranges of a number of characteristic species of the northern 
Sierra is shown in Fig. 42. The Patton hemlock has a restricted and 
uneven distribution following a granite axis on the summit of the range 
over which its distribution corresponds with the belt of heaviest pre- 
cipitation. Its continuity is broken by deep, low valleys. The Shasta 
fir is another essentially mountain species. It appears to require a 
precipitation of at least 50 inches and hence does not occur below ele- 
vations of 4800 feet. Since it is restricted to limited areas because of 
its temperature and moisture requirements, it is not distributed in a 
continuous belt but like the Patton hemlock is broken by deep valleys 
and canyons. The sugar pine has a wider and more continuous dis- 
tribution. It is absent below 2000 feet in the western foothills and 
occurs on the eastern and upper margin of the belt in detached frag- 
mentary bodies and east of the m^ountains almost not at all. The 
yellow pine has the widest range of any of the Sierra species. Its lower 



CASCADE AND SIERRA NEVADA MOUNTAINS 



175 



limit of distribution is about 1500 feet, its upper from 6500 to 7000 feet. 
The high precipitation and low temperature of the summit of the 
Sierra prevent the yellow pine from occupying the higher ridges, just as 
dryness prevents it from occupying the Sacramento Valley. 

Some of the high ridges covered with andesitic breccia are very dry 
and support either no trees or shrubs or those types normally found at 
a lower altitude under drier conditions.^ 




Yellow Pine Sugar Pine Shasta Fir 
Scale of Miles 



Patton Hemlock 



Fig. 42. — Ranges of four characteristic species in the northern Sierra Nevada. 
(Compiled from U. S. Geol. Surv. maps.) 

The trees of the thinner forests below 3000 feet grow in thin groves or 
are scattered over grassy slopes. Yellow pine occurs on the higher ridges 
as an outlying fringe of the great forests of the timber belt, while oaks 
are particularly abundant on dry areas underlain by the older volcanic 
breccias and tuffs. Many hills are thickly covered with an evergreen 
shrub (greasewood), and in the lower part of the belt the Digger pine 

I Turner and Ransome, Big Trees Folio U. S. Geol. Surv. No. 51, 1898, p. 3. 



176 FOREST PHYSIOGRAPHY 

comes in, besides stunted oaks, and a number of shrubs. The lower- 
most zone of vegetation in the foothill belt also contains the Digger 
pine and stunted oaks, and shrubs characteristic of greater dryness, such 
as the manzanita.^ 

Although the forests of the Sierra Nevada are more restricted in 
vertical range toward the south owing to increasing aridity in this direc- 
tion, they persist as far as the 36th parallel, where the elevation of the 
mountains begins to decrease. With lower elevation the rainfall dimin- 
ishes to the point where a stunted vegetation appears, and at the extreme 
south a true desert flora is developed. By contrast, the Coast Ranges 
exhibit a desert vegetation as far north as the Bay of Monterey (lat. 
37°), and nowhere bear extensive forests south of San Francisco. The 
lesser elevation of the Coast Ranges accounts for a large part of this 
deficiency, though a part also must be attributed to their position on 
the margin of the belt of westerly winds. They receive their rainfall 
chiefly during the winter season, when the westerly wind belt with its 
cyclonic storms has migrated southward over them. But the latter 
deficiency is shared by the Sierra Nevada. We may therefore say that 
were the altitudes of the two ranges reversed the Coast Ranges would 
be densely wooded at least as far south as the Bay of Monterey while 
the Sierra Nevada would be practically without forests. 

It seems clear from the topographic character of the Sierra Nevada as 
well as the Cascades that large portions of the existing forests grow 
under conditions that must for a long time to come, perhaps forever, 
prevent the utilization of their products. Especially is this true of 
detached areas of forest on high mountains and steep slopes separated 
from the main body of the forest by deep and almost unscalable can- 
yons and gorges, and far from centers of population upon which the 
lumberman must depend for a labor supply as well as for the consump- 
tion of the forest products. The steep, cliff-hke walls of the larger 
valleys themselves offer difficulties of the highest order. Ordinary 
lumbering methods are useless, extraordinary methods are so expen- 
sive as to make the development of the more difficult forest areas highly 
improbable. The potential value of the forests in the more difficult 
tracts is therefore very limited in relation to the lumber supply, but their 
practical value is almost unlimited in relation to stream flow. The 
retardation of the run-off on steep slopes is a matter of the greatest 
concern where both the rainfall and the snowfall are heavy and the 
topography extraordinarily rugged, and this is everywhere to some 
extent and in some places to a large extent effected by the forest cover. 

1 F. L. Ransome, Mother Lode District Folio U. S. Geol. Surv. No. 63, 1900, p. i. 



CHAPTER XII 

PACIFIC COAST VALLEYS 
General Geography 

One of the larger features of the continent of North America is the 
discontinuous hne of valleys known as the Pacific coast downfold, a 
structural and topographic depression between the Coast Ranges on the 
west and the Sierra Nevada and Cascade mountains on the east. Its 
most striking expression is in the valleys of the San Joaquin and the 
Sacramento in central California and in the Willamette Valley in north- 
western Oregon, where the Coast Ranges descend with marked abrupt- 
ness to the level of the alluvium-filled valley floors. The width of the 
downfold is about loo miles from crest to crest of the bordering ranges 
and from 50 to 75 miles from mountain front to mountain front; the 
total length is about 2500 miles. The northern and southern ends of 
the downfold are submerged, forming Puget Sound and the Gulf of 
CaHfornia respectively; the higher unsubmerged sections extend through 
northern California, Oregon, and Washington and are separated by two 
mountain groups. The divisions are as follows: (i) a southern divi- 
sion extends from Gulf of California to Los Angeles, (2) a central divi- 
sion constitutes the Great Valley of California, and (3) a northern 
division comprises the Willamette Valley in Oregon, the Cowlitz Valley 
in Washington, and the broad depression at the head of Puget Sound. 
The mountains separating the southernmost depression from the Great 
Valley of California are the San Gabriel, San Rafael, San Bernardino, 
and others; those separating the Great Valley of California from the 
Willamette Valley are the Klamath, a group rather than a range of 
mountains, consisting of a number of secondary ranges among which 
are the Siskiyou, Rogue River, and others. 

The Pacific coast downfold has been a feature of the western coast 
since the Cretaceous period, and during several geologic periods was so 
deeply depressed as to lie beneath sea level and receive a considerable 
body of sediments. The later phases of alluviation are due to the 
action of the tributary streams which descend in steep courses from the 
flanks of the high mountains near by and contribute a vast body of 
detrital material to the upbuilding of the valley floors. 

177 



1 78 FOREST PHYSIOGRAPHY 

Willamette, Cowlitz, and Puget Sound Valleys 

The northernmost section of the Pacific coast downfold consists 
chiefly of the Willamette and Puget Sound valleys. The alluvial 
portion of the Willamette Valley heads near Eugene, Oregon, and ex- 
tends north to the Columbia. North of that river the depression is 
continued by the Cowlitz Valley and lesser valleys tributary to the 
southern end of Puget Sound. The depression is important climatically, 
since on the north it lets in the sea in the form of a great mediter- 
ranean that extends 150 miles inland; and in the Willamette Valley on 
the south it results in a much greater seasonal range of temperature 
than occurs in the coastal section near by from which it is separated by 
the Coast Ranges. Everywhere in the northern depression the rainfall 
is markedly less than on the windward (western) slopes of the border- 
ing Coast Ranges and Cascades. 

In Washington the greater part of the depression is composed of 
alluvium and glacial or fiuvio-glacial deposits. These consist of till, 
sand, and gravel, and were formed during and at the close of the glacial 
period when piedmont and valley glaciers descended from the border- 
ing mountains and discharged into the waters of Puget Sound. The 
surficial deposits overlie and partly obscure an older topography, a 
well-developed valley system coordinated with the present system of 
converging sounds and bays so suggestive of the drowning which oc- 
curred here. The postglacial changes are due chiefly to the extension 
of the deltas at the mouths of the streams. These advance into the 
bays, reclaim their heads, and thus greatly modify both valley and 
shore.^ The irregularities of the shore line of Puget Sound are not 
attributable to depression alone. The glaciation of the sound deepened 
and widened the depressions that were the lines of glacial movement, 
but the deepening was so much more important than the widening 
that the channels are deep and narrow. The low water-parting be- 
tween the Cowlitz Valley and the valleys tributary to Puget Sound is due 
to the deposition of alluvium and glacial deposits upon a previously 
nearly level-floored intermontane depression.- 

The Willamette Valley south of the Columbia River is to the Cow- 
litz north of the Columbia what the San Joaquin is to the Sacramento. 
It is intensively farmed, relatively, and is almost unforested in contrast 
to the densely forested, because better-watered, hills and mountains on 

1 Willis and Smith, Tacoma Folio U. S. Geol. Surv. No. 54, 1899, p. 2. 
' I. C. Russell, North America, 1904, p. 160. 



PACIFIC COAST VALLEYS 1 79 

either side. Its deposits are likewise of glacial and fluvial origin, de- 
posits of the latter kind predominating.' The valley is 150 miles long 
and at present constitutes the most important single tract of arable land 
in the state. 

Great Valley or California 

CLIMATIC FEATURES 

In the study of the Great Valley of California, and indeed of the 
physiography of the California district as a whole, one must keep in 
mind the great range in latitude between its northern and southern 
ends. The state is Soo miles long, and if it were transposed to the 
Atlantic seaboard with its southern end placed on Charleston, South 
Carolina, its northern end would lie approximately on New Haven, 
Connecticut. The southern end of California is a region of deserts, 
desert mountains, salt lakes, a sparse and specialized vegetation, and 
other features associated with pronounced aridity. The northern end 
of California lies on the whole in the belt of adequate rains; on the 
windward slopes of the mountains in the northwest corner of the state 
there is a mean annual rainfall of 81 inches,- and dense forests of 
redwood clothe the mountain slopes. 

These great differences in precipitation are due to two conditions: (i) 
the state is of unusual size and has a wide range of latitude; (2) it lies 
partly within two climatic belts, the belt of westerly winds, and the 
horse latitudes. The mean annual rainfall varies from i inch to 81 inches. 
In the extreme southern part of California there live many people who 
have never seen snow in any form. At Summit, near Donner, in 
northern California, an annual snowfall of 697 inches, or nearly 60 feet, 
has been reported. Farming is conducted in an ordinary manner in 
large sections of northern California, though some irrigation is prac- 
ticed; irrigation is the indispensable condition of the agriculture and the 
horticulture of southern California. Little wonder is it that under these 
circumstances Californians should speak of northern California and 
southern California as two very unlike regions. The degree of unlike- 
ness is so extreme, the different interests so divergent in many respects, 
that the idea is quite widely entertained that California should be sep- 
arated into two states for the better safeguarding of local interests. 

In addition to the climatic differences between northern and southern 
California are east-vv^est differences of climate dependent upon strong 

1 For the character of the drainage and the topography of the upper Willamette Valley see 
the Eugene quadrangle, U. S. Geol. Surv. 

2 A. J. Henry, CHmatology of the United States, Bull. Q, U. S. Weather Bureau, igo6, 
pp. 9-72. 



i8o FOREST PHYSIOGRAPHY 

contrasts in the different north-south belts of relief. These are sum- 
marized by Hilgard ^ as follows : 

(i) Bay and coast region characteristics: Small range of temperature, the extremes being 
only 53° apart. Means of summer and winter are only 6° apart. There is no' intense heat 
and frosts are very rare. Fogs from the sea are quite common on summer afternoons. Rain- 
fall averages 27.3 inches, about 25 inches of which falls between December and May. 

(2) Great Valley characteristics: Average winter temperatures lower than those of the 
coast, though minimum is about the same. Frosts are rare. Summer heat is very intense, 
often above 100°. The nights are warm but dry, and are therefore less oppressive. Extreme 
range of temperature 76°, mean range 23.6°. Rainfall averages about 21.5 inches, of which 
19.8 inches fall between December and May. 

(3) Sierra slope characteristics: Cool summers with frequent thunderstorms. The winters 
are often severe, with much rain and snow. Mean summer temperatures, 57.5°, with a mean 
range of 14° between that and the winter temperature of 43.5°. Rainfall averages 57.24 inches, 
fairly well distributed throughout the season. 

GENERAL GEOGRAPHIC AND GEOLOGIC FEATURES 

The Great Valley of California, the largest unit of the great Pacific 
coast downfold, lies between the two main chains of that state, the 
Sierra Nevada on the east and the Coast Ranges on the west. It is 
about 400 miles long, has an average width of about 50 miles, and 
contains about 20,000 square miles. It consists chiefly of two long and 
relatively narrow piedmont alluvial plains with a monotonously level 
surface and a marked parallelism with all the main physiographic 
features of the state lying north of the 35th parallel. 

The drier southern end of the Great Valley is a region of large wheat 
ranches, but in later years fruit raising has begun to supplant this 
industry. Grazing is also a principal resource. The better-watered 
northern end of the valley produces lumber, dairy products, fruits, and 
vegetables; and the greater rainfall of the Sacramento Valley and border- 
ing ranges so well maintains the level of the Sacramento River that a 
navigable depth of seven feet from Sacramento to the river's mouth is 
maintained at slight expense. ^ 

The history of the Great Valley dates from the great orogenic disturbance at the close of the 
Miocene which gave birth to the Coast Ranges as a connected mountain chain. Later still 
(at the close of the Pliocene) the Sierra Nevada block was further uplifted and the Coast Ranges 
increased in height, an increase which has continued down to the present time.^ During the 
post-Pliocene elevation of the crest of the Sierra and of the Coast Ranges and also in the 
Pleistocene period the Great Valley was gradually and finally cut off from the sea, closed in 
by mountains, and changed to a deSnite well-bounded area of sediments, upon which stream 

1 E. W. Hilgard, quoted by Van Winkle and Eaton, Quality of the Surface Waters of Cali- 
fornia, Water-Supply Paper U. S. Geol. Surv. No. 237, 1910, pp. lo-ii. 

2 Document No. 1123, 60th Congress, 1909. 

' F. L. Ransome, The Great Valley of California, Bull. Dept. Geol., Univ. Cal., voL i, 
1896, p. 387. 



PACIFIC COAST VALLEYS l8l 

deposits began to form. The whole Great Valley is now completely walled in by mountains 
except where the Sacramento and San Joaquin unite to flow through the straits of Carquinez 
into San Francisco Bay. 

The Great Valley is divided into three parts: (i) the Sacramento 
Valley, drained by the Sacramento River; (2) the San Joaquin Valley, 
drained by the San Joaquin River; and (3) the Tulare Valley, which might 
be considered a subdivision of the San Joaquin Valley, for it is sometimes 
tributary to it. 

SACRAMENTO AND SAN JOAQUIN VALLEYS 

The Sacramento Valley is a broad and nearly flat alluvial plain. 
It gradually diminishes in breadth northward and terminates near 
Red Bluff at an altitude about 300 feet above the sea. At this point 
the valley is composed of low alluvial fans which have developed to 
the point of confluence. On the western side of the valley the moun- 
tain slopes rise abruptly from the plain; on the east the slopes of the 
Sierra Nevada rise in a more regular and even manner. All the streams 
from the Sierra Nevada that enter the Great Valley carry large amounts 
of rock waste and those that drain the largest basins carry exceptionally 
large amounts. Their gradients are greatly decreased as they emerge 
from their deep mountain canyons, and a part, sometimes a large part, 
of their water is absorbed or evaporated. Thus the carrying power of the 
streams diminishes rapidly, and eventually a part of the load of land 
waste is dropped in the form of alluvial fans some of which are 40 to 
50 miles in radius. The alluvial fans are composed of coarse waste 
near the mountain foot, — rough, bowldery material, very pervious, and 
therefore very dry. Farther from the mountains the material becomes 
finer; on the lower valley flats it is chiefly fine silt. 

Across the broad plain of gravel and sand which forms the northern 
end of the Sacramento Valley the river and its tributaries have cut 
valleys from one-fourth mile to four miles in width and to depths some- 
times reaching 100 feet. The floors of the valleys are generally flat and 
may be called the valley flats and flood plains of the adjacent streams. 
They are covered with fine alluvial soil which when well watered is 
excellent for agricultural purposes.^ 

The tributaries of the Sacramento before reaching the main stream 
turn aside and discharge in stagnant sloughs which expand and over- 
flow large areas during the wet season. Broad belts of swamp land 
and lake therefore occur on both sides of the Sacramento River and are 
usually covered by a dense growth of tule (Scirpus lacustris). The 
plains and the lowest rolling foothills are on the whole without arboreal 
' J. S. Diller, Redding Folio, U. S. Gaol. Surv. No. 138, 1906, p. 1. 



l82 , FOREST PHYSIOGRAPHY 

vegetation save for scattered oak trees which give a park-like character 
to the landscape. The river is usually lined by tule swamps and the 
banks support a dense vegetation of brush and willows.^ Farther south 
the Sacramento River and its principal tributary, the Feather River, 
flow in channels well above the general level of the flood plain. The 
case of the Yuba River is of peculiar interest. Mining operations in its 
valley have caused the delivery to the stream of an exceptional amount 
of alluvium, so that the town of Marysville, which was formerly well 
above the river, is now considerably below it at high water. 

The streams draining the western slopes of the Sierra Nevada con- 
stitute the larger part of the drainage of the Sacramento Valley and have 
a relatively constant flow reaching the Sacramento through definite 
channels; the smaller streams draining the eastern slopes of the Coast 
Ranges seldom reach the Sacramento River at the surface but are lost 
in the intricacies of the sloughs which meander through the border- 
ing tule lands. This difference in the amount of water and therefore of 
alluvium contributed to the Sacramento and the San Joaquin valleys 
on the east and west sides has resulted in a marked asymmetry of vaUey 
form, both rivers lying on the western sides of the plain. The San 
Joaquin, especially, flows close to the base of the Coast Ranges, having 
been pushed farther and farther west by the building up of low conflu- 
ent alluvial fans at the mouths of the Sierra streams. In a similar way 
Lake Tulare lies near the western edge of the valley on account of the 
encroachment of the extensive fan of the Kaweah River combined with 
the deltas of the Kings River and other streams. 

On the north the alluvial portion of the Sacramento Valley is bordered 
by a well-marked plain of erosion (Pliocene) which passes under the 

Klamath _ . „ ,, 

—^Mountain Sacramento Valley 

'^l'>S?f^?5'^>T--r-'t' ^°° f^y- ., ,„,, Base leveled suiface 6oo ft. 

7 6 6 6 5 5 A i A 3 'i 

SECTION NEAR ELDER CREEK7TEHAMA CO. 
FaII-=) 30 feet per mile 

Fig. 43. — Base-leveled plain on the northern border of the Great Valley of California. 
(Diller, U. S. Geol. Surv.) 

lavas of the Lassen Peak district and in some places changes gradually 
and in others abruptly into the mountain slopes of the Klamath region. 
It is considered to be a continuation of the peneplain recognized within 
that region. The width of the base-leveled plain at the northern end 
of the valley varies from one to fourteen miles, and was once part of 
an extensive erosion plain which formerly included middle and northern 
> Lindgren and Turner, Marysville Folio U. S. Geol. Surv. No. 17, 1895, p. i. 



PACIFIC COAST VALLEYS 1 83 

California, southern Oregon, and possibly an even greater area. The 
plain cuts across Cretaceous and Tertiary strata along the eastern border 
of the northern part of the Sacramento Valley. These strata pass by 
gentle dips westward beneath the valley and rise again to the surface 
along the western border, thus outlining the northern part of the valley 
as a broad shallow geosyncline filled with deposits of late geologic age.^ 

TULARE VALLEY AND LAKE 

Tulare Valley, near the southern end of the Great Valley of Cali- 
fornia, contains Tulare Lake, which has no regular surface drainage to 
the sea. The waters of the lake are separated from the San Joaquin 
system by a gentle swell of alluvium, so that in seasons of unusual rain- 
fall a surface connection is established between the lake and the river. 

The combination of drainage conditions about Lake Tulare reminds 
one very strikingly of those in the Salton Sink region. The basin of 
Lake Tulare is due chiefly to the building up of alluvial fans across the 
San Joaquin Valley north of it, especially between Kings River on the 
east and Los Gatos and other creeks in the northern part of the Coalinga 
district, the latter having formed exceptionally large alluvial fans for 
Coast Range streams. Lake Tulare is therefore a broad shallow v*^ater 
body developed upon an almost level floor of alluvium and represents 
an expanse of water above an obstructing dam formed by alluvial fans. 
It derives its water supply from several streams that descend from the 
Sierra Nevada and spread numerous distributaries over the valley floor. 
Practically no surface water reaches the lake from the mountains on 
the west side in spite of their closer proximity. On all sides the lake is 
bordered by broad tule-covered swamps, hence its name. 

Lake Tulare has no regular surface outlet; the water level is con- 
trolled by seepage and evaporation. It is therefore subject to great 
fluctuations and in periods of high water the whole central portion of the 
valley becomes flooded and marshy. In earlier years the lake was one 
of the largest bodies of fresh water in California; in later years it has 
been gradually declining in size owing largely to decreased rainfall, to 
the use of the water of its tributary streams for irrigation, and to the 
reclamation by dikes of the land formerly covered by it. In 1880 it 
overspread an area about 27 miles long and 20 miles wide; in 1889 it 
was 20 miles long and 15 miles broad. Still more recently successive 
dikes have been constructed, the lake has almost dried up, and most of 
the former lake bottom has been cultivated. In 1907 the precipitation 

I A. C. Lawson, Bull. Dept. Geol., Univ. Cal., vol. i, 1896, p. 271. 



1 84 FOREST PHYSIOGRAPHY 

was unusually large and the whole central portion of the valley was again 
inundated, the lake extending almost to its old shore line of 1880 near 
the base of the Kettleman Hills bordering the Coast Ranges. 

During late Quaternary time Tulare was much greater than at present, as shown by an 
old beach a hundred feet above it. The beach is in the form of a ridge of sand about 20 feet 
wide, 6 to 8 feet high, and somewhat eroded and covered with vegetation. A line of depression 
across the middle of the main valley connects Tulare Lake by a low marshy tract with tv;o 
smaller lakes, Kearn and Buena Vista, 50 miles to the south, which owe their position near 
the base of the Coast Ranges to the westward growth of the large delta of the Kearn River. 1 

Valley or Southern California 

LOCATION AND CLIMATIC FEATURES 

The valley of southern California is a lowland area limited on the 
north by the San Gabriel range and separated from the Mohave and 
Colorado deserts on the east by the San Bernardino and San Jacinto 
mountains. On the west the plain extends to the Pacific; on the south 
its limits are irregular and indefinite, a broad transitional belt occurring 
between it and the heights of the Sierra Madre of Mexico. It is not a 
part of the great Pacific downf old but a separate lowland unit. The val- 
ley of southern California is more populous, more intensely cultivated, 
and has more concentrated wealth than any similar area in the South- 
west. These unique features depend upon its climate, its fertile soil, 
and its valuable products. Its southerly position gives it a moderately 
high mean annual temperature of about 62°. The open exposure of its 
surrounding mountains to the Pacific results in a marked rainfall and 
hence they supply more water for irrigation than is commonly supplied 
to the alluvial plains of the West. The streams that descend form the 
seaward slopes of these mountains and water the alluvial plain between 
them and the sea are, as such streams go, of great size and permanence 
of flow. The soils are generally well disintegrated arid land soils with 
a high percentage of soluble plant food. 

TOPOGRAPHY AND DRAINAGE 

The valley of southern California, Fig. 44, is divided by the Santa Ana 
Mountains and the Puenta Hills into two parts: (i) a coastal portion, 
the coastal plain, and (2) an interior portion, the interior valley. The 
coastal plain of southern California is about 50 miles long and 15 to 20 
miles wide. Its relief is in general low and the regional slope is seaward 

I Arnold and Anderson, Geology and Oil Resources of the Coalinga District, Cahfornia, 
Bull. U. S. Geol. Surv. No. 398, 1910, pp. 39-382. 



PACIFIC COAST VALLEYS 



185 




i86 



FOREST PHYSIOGRAPHY 



from an elevation of 200 to 300 feet along the inner margin to the salt 
marshes and sand dunes of the coast. The chief interruptions of its level 
surface are San Pedro Hill and a low ridge that extends southeastward 
from the vicinity of Palms. The inner edge of the coastal plain forms 
a fringe of bench land which contours the higher mountains back of it 
and forms bluffs except where the mountains approach the coast. It 
is somewhat dissected by the canyons of the small streams that cross 
it. These gullied benches are conspicuous back of Santa Monica and 
along the southern base of the Santa Monica Mountains, where they are 
composed of stream-deposited sands, gravels, and clays, in contrast to 




Fig. 45. — Inner edge of the coastal plain of southern California near Whittier. 
(Mendenhall, U. S. Geol. Surv.) 

the marine deposits which make up a large part of the coastal plain. ^ 
The coastal plain of southern California is regarded as a former broad 
embayment of the Pacific in which debris brought down by the 
mountain streams accumulated; it was finally exposed by uplift and 
slightly modified by erosion. ^ 



FORESTS AND WATER SUPPLY 

In southern California, where water supply is a dominating economic 
necessity, a very intimate relation has been found to exist between 
the amount of forest cover in the mountains and the water supply 

1 W. C. Mendenhall, Development of Underground Water in the Western Coastal Plain 
Region of Southern Cahfornia, Water-Supply Paper U. S. Geol. Surv. No. 138, 1905, pp. 9-11. 

2 Idem, p. II. 



PACIFIC COAST VALLEYS 



187 





Fig. 46. 



■West Rivcrsiile district, California, rcprusenting typical relations of mountains and bordering 
alluvial plains, valley of southern California. (Mendenhall, U. S. Geol. Surv.) 




Fig. 47- 



• West Riverside district, California. This view is panoramic with the one above. The moun- 
tain notch on the right is the notch on the left in Fig. 46. 



l88 FOREST PHYSIOGRAPHY 

of the bordering plains. The matter is of great importance to horti- 
cultural interests in southern California because of the nearly rain- 
less summer, the precipitation occurring almost wholly in the winter 
months from November to April. Practically all of the rain that falls 
upon the flat porous valley lands is immediately absorbed by the soil 
or evaporated into the air. On the mountain slopes a large propor- 
tion is absorbed by the soil and humus where vegetation has not been 
destroyed by fire and the unprotected soil swept off. It is the water 
absorbed by the soil and forest litter of the mountain slopes that is the 
source of the important summer flow of the mountain streams. It has 
been found that the denser the vegetal growth and the thicker the soil 
on the mountain slopes, the more effectively are the winter rains stored 
and the more uniform is the summer flow. The effect of the forest in 
decreasing surface flow during the rainy season is enormous, the average 
of four different basins showing an absorption of 95% on the forest- 
covered areas and only 60% on the nonforested areas, where the 
rainfaU is much less. A comparison of three other areas gave the 
following result: 

"The three forested catchment areas, which, during December, experienced a run-off of but 
5% of the heavy precipitation for that month and which during January, February, and March 
of the following year had a run-off of approximately 37% of the total precipitation, experienced 
a well-sustained stream flow three months after the close of the rainy season. The nonforested 
catchment areas, which during December experienced a run-off of 40% of the rainfall and which 
during the three following months had a run-off of 95% of the precipitation, experienced a run- 
off in April (per square mile) of less than one-third of that from the forested catchment areas, 
and in June the flow from the nonforested area had ceased altogether." 1 

The disastrous results that follow deforestation are of great concern in 
this thinly forested region, for the private lands are being rapidly defor- 
ested by large lumber camps, whose operations cause ever-increasing 
danger from forest fires, floods, and summer droughts. ^ 



Soils of the Pacific Coast Valleys 

The soils of the Pacific coast valleys range from residual and colluvial 
soils of the mountain foothills to deep and extensive river flood-plain 
and delta sediments and ancient and modern marine and lacustrine 
shore deposits. The wide range in value of these soils and their adapta- 

1 J. W. Toumey, The Relation of Forests to Stream Flow, Yearbook, Dept. of Agri., 1903, 
pp. 286-287. 

2 Van Winkle and Eaton, Quality of the Surface Waters of California, Water-Supply Paper 
U. S. Geol. Surv. No. 237, 1910, p. 17. 



PACIFIC COAST VALLEYS 



189 



tion to crops is dependent largely upon the possibilities of irrigation and 
upon local climatic conditions of rainfall and temperature. 

The soils of the alluvial fan deposits, colluvial and alluvial wash 
from foothills and higher adjacent soil bodies, and occasional small areas 
of residual material are derived mainly from sandstones, shaly sandstones, 



120° 







Fig. 4S. — Irrigation map of the West. Irrigated areas solid black, irrigable areas dotted. 
(Newell, Irrigation in the U. S.) 



and shales (Cretaceous and Tertiary), and occur upon rolling marginal 
hills, sloping, elevated, and dissected mesa or bench lands, and in some 
places on the margins of lower nearly level valley plains. 

The soils composed of recent alluvial materials derived from a great 
variety of rocks and deposited as river and delta plains generally occupy 



IQO FOREST PHYSIOGRAPHY 

a lower topographic position, are of more recent origin, are subject to 
more frequent overflow than other soils of the region, and often support 
a growth of swamp vegetation, brush and willow thickets, and timber 
in the river bottoms and lower valley plains. The surface is generally 
level, shghtly sloping or sometimes uneven, and is frequently marked 
by sloughs or the interlacing channels of streams many of which carry 
water only in times of flood and disappear in sandy washes. The heavier 
members are frequently marked by adobe structure and the soils are 
generally free from gravel or bowlders. 

The lower-lying areas are frequently poorly drained, subject to the 
influence of seepage water from irrigation, and contain alkali. They 
are generally underlain by subsoils of fine ashy texture, light color, and 
compact, close structure, usually separated from the overlying soil by 
an alkali carbonate hardpan of white or light-gray color. The hardpan 
softens slowly upon the application of irrigation water, but is normally 
impenetrable to the roots of growing plants. 

An important group of soils is composed of alluvial deposits formed by 
shifting streams and mountain torrents and occurring as broad, low, 
alluvial cones occupying gently sloping plains or slightly rolling valley 
slopes, generally treeless and lying above present stream flood plains. 
The soils of this series are derived from a variety of rocks, but generally 
from those of granitic and volcanic character, or from sandstones carry- 
ing large amounts of granitic material. They are generally treeless and 
support only a desert vegetation except where they are irrigated. They 
are frequently cut by arroyos, and are usually gravelly and often strewn 
with bowlders. These soil bodies vary from small areas of irregular 
outline to broad, extensive, uniform sheets. They are generally dark- 
colored, open-textured, well drained, and free from alkali. 

The Great Valley contains no true forest growths, only lines of poplars 
and sycamores along the rivers. The lower foothills on the borders of 
the valley and up to elevations of looo feet are dotted with Douglas 
oak and live oak and occasional patches of a thorny shrub (Ceanothus 
cuneatus). During the dry summer season the main expanse of the 
valley presents a rather monotonous and cheerless view since it is prac- 
tically treeless and covered with a dry gravelly soil or a parched growth 
of sparse grasses that spring up in the wet season. Along the stream 
courses in the axis of the valley trees are sometimes found, though willow 
and alder shrubs are more common growths.^ 

The soils of the valley of southern California are similar in origin, 
topographic position, and texture to those of the Great Valley. The 

1 Turner and Ransome, Sonora Folio U. S. Geol. Surv. No. 41, 1897, p. 3. 



PACIFIC COAST VALLEYS 19I 

most important departure from the general character is made on the 
coastal plain. Its outer margin has soils of distinctive character derived 
from marine sediments. Except along stream courses and at the heads 
of some of the alluvial fans arboreal vegetation is entirely wanting. 

In the Tacoma region at the northern end of the series of coast 
valleys the bottom-land soils of the valley floors are stream-laid and vary 
in texture from gravel to fine silt. Silt is most common, gravel and sand 
have a more restricted development and are generally found near the 
mouths of the canyons and at the heads of the alluvial fans of tributary 
streams. 

The soils of the uplands are disposed on steep sharp ridges and washed 
to such a degree as to be unfit for tillage, except in limited areas on 
rounded hills. Locally the soil is open in texture and very sterile, as in 
the case of the Steilacoom plains south of Tacoma. Although these plains 
receive about 44 inches of rain per year, the water drains away so rapidly 
in the loose, stony ground that they are an arid tract in the midst of a 
humid region.^ 

The primeval growth of the valley soils was fir and hemlock with 
cedar and maple predominating in the wet lands along the hollows and 
tributary gullies. 

> Willis and Smith, Tacoma Folio U. S. Geol. Surv. No. 54, 1899, p. 7. 



CHAPTER XIII 

COLUMBIA PLATEAUS AND BLUE MOUNTAINS 



_/-\ _^5° I 



COLUMBIA PLATEAUS 
Extent and Origin 

The Columbia physiographic province includes a large variety of 
physical features whose basis of unity lies in their common association 
with those widespread sheets of balsaltic lava that form the larger part 
of the region. It is important therefore to have at the outset a clear 

conception of the geologic ori- 
gin and nature, areal extent, 
and physiographic features of 
the Columbia River and Snake 
P-iver lavas. 

In sharp contrast to the 
mountainous borders of the 
province are the fiat or appar- 
ently flat basalt plains which 
cover an area of over 250,000 
square miles and form prob- 
ably the most extensive single 
field of sensibly flat basalt in 
Their development 
involved the transference of 
about 100,000 cubic miles of dense rock from the earth's interior to 
the surface. For many years all these basaltic flows were believed to 
have originated from fissures concealed by the lava that issued from 
them. This was the view of Sir Archibald Geikie, for example, when 
in 1S82 he described the Snake River basalt plains.^ But the studies 
of Russell have shown conclusively that no direct evidence has been 
found in support of this explanation in the greater part of the Snake 
River lavas, while the region abounds in evidence pointing to the local 
accumulation of material from a large number of vents of several varie- 
ties. In many localities low mounds may be seen rising by gentle 

1 Sir Archibald Geikie, Geological Sketches at Home and Abroad, 1882, pp. 237-242 

192 




Fig. 4g. — - Lava fields of the Northwest. (Data from Geo- .1 ij 

logic Map of North America, by Willis, U. S. Geol. Surv.) 



COLUMBIA PLATEAUS AND BLUE MOUNTAINS 1 93 

gradients above the general level of the country. Their summits are flat, 
and from them may be traced lava flows which extend outward in all 
directions until they merge into the flat expanses of the plain. Here and 
there on the borders of the region flows may be traced down tributary 
valleys at whose mouths they expand to form part of the general surface. "^ 

To produce so flat and so extensive a plain, lava must have great 
fluidity and must originate from separate vents thickly strewn over a 
given region. Both these conditions are fulfilled here. Vents are numer- 
ous and their flows have been traced into each other to such an extent 
that the region may be described as consisting of a large number of low 
gradient plains merging inperceptibly into each other. Some of the 
constituent minerals of the basalt (augite, etc.) fuse at such low tem- 
peratures that a high degree of fluidity had been attained by the lava. 
It ran readily over the gentle slopes and spread far and wide before 
it was congealed. Were the flows less fluid they would have gathered 
closer about the volcanic vents and would now show far steeper gradi- 
ents, as in the Cascades. 

While the Snake River lava was thus formed by volcanic extravasa- 
tion of highly fluid material from many different vents, the basalt of a 
large portion of eastern Oregon and Washington is equally well known 
to have originated from a vast number of fissures. On the eastern 
border of the Cascades there is a great system of feeding dikes in the 
sandstone beneath the basalt; similar relations have been observed in the 
Blue Mountains, where the once overlying basalt has been removed by 
erosion.^ 

In central Idaho on the eastern edge of the basalt plain east of Lewiston no ash cones or 
tuff volcanoes are found nor are any dikes of basalt observed in the foothills of the Clearwater 
Mountains adjacent to the basalt. The eruption of the fluid rock must have taken place in 
this locality without explosive action and from fissures.^ In the Eagle Greek range, Oregon, 
a local center of eruption has been discovered near Cornucopia, where at elevations of 7000 to 
8ocx3 feet there occurs a perfect network of basalt dikes intersecting the schists and granites 
immediately above the lava plateau.* 

The lavas comprising the Snake River and Columbia River plains are 
of two general sorts, basalt and rhyolite. The basalt, as we have al- 
ready seen, was spread over the surface in great flows and in a highly 

• I. C. Russell, Geology and Water Resources of the Snake River Plains of Idaho, Bull. 
U. S. Geol. Surv. No. 199, p. 66. 

2 F. C. Calkins, Geology and Water Resources of a Portion of East-Central Washington, 
Water-Supply Paper U. S. Geol. Surv. No. 118, 1905, p. 19. 

2 W. Lindgren, A Geological Reconnaissance Across the Bitterroot Range and Clearwater 
Mountains in Montana and Idaho, Prof. Paper U. S. Geol. Surv. No. 27, 1904. 

* W. Lindgren, The Gold Belt of the Blue Mountains of Oregon, 22nd Ann. Rept. U. S. 
Geol. Surv., pt. 3, 1902, pp. 740-745. 



194 FOREST PHYSIOGRAPHY 

fluid condition. The rhyolite, on the other hand, was extruded in part 
in the form of sheets or flows and part as ejectamenta — volcanic dust, 
gravel, lapilli, and other angular fragments. These two kinds of erup- 
tions occurred at different periods; the greatest inundations of basaltic 
lava in eastern Oregon took place before the rhyolitic eruption. After 
the rhyolite had been extruded there came a renewal of the basaltic 
eruptions, which continued from time to time almost to the present day 
but on a far less extensive scale. The latest basaltic eruptions of the 
Snake River plains are so fresh as to appear to have been formed within 
historic times, probably not more than several hundred years ago; the 
earliest eruptions date back to the Tertiary (Miocene). The total 
number of flows varies from place to place, but in a number of cases at 
least ICO are known to have occurred. 

There is considerable difference in the age of the Columbia and the 
Snake River lavas. The Columbia River lava is deeply decayed and 
over large areas has been changed to a soft clay-like soil having a depth 
of sixty feet or more, while the Snake River lavas are still fresh and 
even the exposed portions of older sheets show but slight changes.^ 

The volcanic outpourings of the region were not limited to the Columbia and the Snake River 
valleys; they extend into the Cascades, which are in large part formed of volcanic material; 
the southern Cascades are almost exclusively volcanic. The greater part of the eastern 
border of these mountains is completely buried beneath recent flows. The basaltic flows also 
extend northward into Canada, where they form a considerable portion of the Interior Plateau 
of British Columbia. Lava flows of the same kind and approximately the same age are found 
in many other localities in the PaciTic Cordillera, as in the Great Basin and the Colorado Plateaus, 
where they form highly important elements of the relief. 



Buried Topography beneath the Basalt 

To understand the present distribution of the lava of the Columbia 
Plateaus and the detailed character of the surface one must know that 
before the lava was extruded the region had considerable relief; canyons 
and gorges had been cut, and the whole surface was in a state of vigor- 
ous dissection. The country rock consisted of old volcanic and sedi- 
mentary formations, mainly granite, rhyolite, quartzite, and lim_estone.^ 

The effect of the basaltic inundations was to fill the valleys and, to 
a large extent, to bury the older topography. In some cases hills and 
mountains of older material project through the basalt as islands pro- 
ject above the surface of the sea, for example. Big, Middle, and 

1 I. C. Russell, Geology and Water Resources of the Snake River Plains of Idaho, Bull. 
U. S. Geol. Surv. No. 199, 1902, p. 61. 

2 Idem, p. 15. 



COLUMBIA PLATEAUS AND BLUE MOUNTAINS 



195 



East Butte, Idaho."^ In other cases the old divides extend for long 
distances into the lava fields as capes and promontories against which 
the basalt came to rest. 
An excellent locality for the study of the relations of the present to 




Fig. so. — Canyon of the Snake River at the Seven Devils. Sketch contours, interval approximately 
SCO feet. The cross-lined areas represent basalt-covered surface; the blank areas represent older 
slates, schists, etc. (After Lindgren, U. S. Geol. Surv.) 

the buried topography is northeast of the Blue Mountains, Oregon, 
where the Snake River has cut a gorge across a great structural arch 
in the basalt and has exposed successive flows with their interstratified 

I I. C. Russell, Geology and Water Resources of the Snake River Plains of Idaho, Bull. U. S. 
Geol. Surv. No. igg, 1902, p. 62. 



196 FOREST PHYSIOGRAPHY 

beds of dust and lake deposits. Near the Seven Devils, Fig. 50, the 
gorge is 4000 to 6000 feet deep, and is one of the most remarkable 
erosion features in the United States. It extends northward for 125 
miles as far as Asotin, a few miles above Lewiston, and is comparable 
in grandeur and depth to the canyon of the Colorado. Above Asotin 
the canyon of the Snake River becomes deeper and furnishes many 
striking illustrations of columnar basalt which rises tier on tier more 
than 3000 feet. Near Buffalo Rock may be seen to best advantage the 
relations of the old and now buried topography to the basalt cover. 
The metamorphic rocks which formed the surface of the country before 
the basalt inundated it rise at least 2000 feet into the horizontally bedded 
flows. The river has thus cut its gorge across a buried mountain and 
has exposed the rocks composing it for a stretch of about a mile. The 
undisturbed horizontal layers of basalt abut sharply against the steep 
waste-free slopes of the old mountain which descend to the lowest level 
of the Snake River and have ancient valleys coordinated with them 
deeper than the present deep canyon of the Snake. ^ The crest line of 
the buried mountain is rugged and serrate; the gorges between the 
higher crests and spurs are filled with horizontal sheets of lava, show- 
ing that the flood of basalt flowed about the highest peaks and for a 
time left them as islands in a molten sea of rock, then overtopped their 
summits and completely buried them.^ The topographies of the can- 
yon wall above and below the contact of these two rock types are very 
dissimilar. The buried surface developed upon the older rocks is ex- 
ceedingly irregular and steep, the spurs ending in precipices that are 
sometimes almost a thousand feet sheer. On the other hand the dull- 
brown and relatively flat-lying basalt is weathered into cliff and talus 
and a more regular type of topographic architecture. 



Drainage Effects or the Basalt Floods 

SNAKE RIVER VALLEY 

The repeated and extensive outpourings of lava resulted in wide- 
spread hydrographic changes. The ancestral Snake River was dammed 
by lava flows to such an extent that a large lake, so-called Lake 
Payette, was formed, upon whose floor sediments were laid down. 
The lake appears to have been invaded time and again by contempo- 

1 I. C. Russell, A Reconnaissance in Southeastern Washington, Water-Supply Paper U. S. 
Geol. Surv. No. 4, 1897, p. 31. 

2 Idem, p. 35. 



COLUMBIA PLATEAUS AND BLUE MOUNTAINS 



197 



raneous lava flows, and it is with these flows and with the widespread 
sheets of volcanic sand and dust that the sediments are associated. 
The lake beds filled the valley to a great depth, and are divided into 
an older (Miocene) and a younger (Pleistocene) division which carry 
mammalian remains and fresh-water mollusks.'^ 

The waters of Payette Lake entirely surrounded the Owyhee range of Idaho, as is shown on 
the west side of this range where the nearly horizontal soft sandstones and shales of lacustral 
origin rest against eruptives (Miocene) and display a well-defined shore line from 5400 to 5500 
feet above sea level. This shore line is also identified along the Boise River but at 1000 feet 
higher elevation, and indicates by its variable elevation at many points in the Snake River 
Valley that notable deformation has taken place since deposition of the lake beds. 

In addition to the main Miocene lake there were formed many small 
lake basins caused by lava dams at the valley mouths, as in Long Valley 
in the northern part of Boise County.- 

The present valley of Snake River extends across Idaho in a semi- 
circular course about 80 miles wide. Its course is underlain by lake 




Fig. 51. — South shore of Malheur Lake, Oregon. Sala.cornia growing in alkali. 
(Russell, U.S. Gaol. Surv.) 



beds and intercalated flows of basalt that slope gently from the border- 
ing mountains to the axis of the valley. Into these beds the river 
has cut a sharp canyon 400 to 1000 feet deep, thus exposing the strvic- 
ture. The average elevation of the Snake River plains of Idaho is from 

1 W. Lindgren, The Gold and Silver Veins of Silver City, De Lamar, and Other Mining Dis- 
tricts, Idaho, 20th Ann. Rept. U. S. Geol. Surv., pt. 3, 1898-gg, p. 80. 

2 Idem, pp. 95-96. 



198 FOREST PHYSIOGRAPHy 

3975 feet at Shawnee to 2125 feet at Weiser. Alluvial and to some 
extent irrigated bottom lands occur at a number of places along the 
river, and they also exist along the lower courses of the Boise and 
Payette tributaries.^ 

HARNEY-MALHEUR SYSTEM 

In Oregon the course of the Malheur River has been profoundly modi- 
fied so as to bring about a loss of fully one-third of its former drain- 
age basin. A lava flow dammed its channel in the vicinity of Mule 
River and caused the formation of the basin of Harney and Malheur 
lakes, Fig. 52. The surface of the lava is only about 10 or 15 feet above 
the normal level of Malheur Lake, and so delicately are the topographic 
and climatic conditions balanced that a very slight increase in rainfall 
would result in the discharge of Malheur River down the line of its old 
valley. The occurrence has additional interest in that the ponding of 
the water above the lava dam causes the entire region now draining into 
Harney and Malheur lakes, about 4500 square miles in area, to be re- 
moved from the Pacific slope drainage and added to the drainage of 
the Great Basin. 

A further modification of the Harney-Malheur drainage has been 
brought about by the formation of hills of wind-drifted sand which 
invaded what was once a single basin, making the two basins now occu- 
pied by Malheur and Harvey lakes. The hills are in part grass- covered, 
with steep-sided basins among them, and furnish a barrier between the 
two lakes which is only crossed by the water of Malheur Lake during 
high- water stages. 

Deformations of the Basalt Cover 

Although the basalt plains of the Columbia region were formed in a 
nearly horizontal position and although these plains appear to be 
approximately horizontal to-day, there are in reality many important 
departures from horizontality. The Snake River plains are now in the 
form of a broad trough or downfold reaching from Lost River and 
Sawtooth Mountains on the north to Goose Creek and Bear River 
Mountains on the south. Many minor irregularities of structure have 
been noted. In southwestern Idaho the lavas and intercalated lake 

1 W. Lindgren, The Gold and Silver Veins of Silver City, De Lamar, and other Mining 
Districts in Idaho, 20th Ann. Kept. U. S. Geol. Surv., pt. 3, 1898-gg, p. 77. See this author's 
geologic map, Plate 8, p. 76, for the distribution of the various types of rocks found in a little- 
known section of central Idaho south of the National Forest that lies east of Mount Idaho 
and northeast of the Snake River Valley. 



COLUMBIA PLATEAUS AND BLUE MOUNTAINS 



199 




200 FOREST PHYSIOGRAPHY 

and river sediments have been gently flexed and, near the bases of the 
bordering mountains, broken and faulted.^ These structural irregu- 
larities are of considerable economic importance, for it is upon the 
trough-like arrangement of the beds that the artesian condition of the 
deeper waters depends. The economic development of the region has 
been accomplished to a notable extent by the use of artesian waters 
for domestic purposes and for supplying stock as well as for a small 
amount of irrigation. 

The existing relation of drainage to relief implies antecedent con- 
ditions on the part of the streams. The lava, originally disposed in 
an essentially horizontal position, has been deformed from this position 
but the deformation has not proceeded so rapidly as to rearrange the 
drainage courses Stream courses laid out upon the nearly, flat lava 
sheets in response to the initial slopes have persisted in their courses, 
and where there have been great uplifts athwart the streams we now 
find great canyons. The explanation is similar to the one applied to 
the present course of the Columbia across the Cascades except that in 
the Cascades it was a base-leveled and to some extent a lava-covered 
surface and not exclusively a sheet of lava that was uplifted across the 
path of the river. Had the lava been in its present attitude when the 
Snake River first gained its course the river would now run in an 
opposite direction for some distance south of the great canyon. 

Coulees of the Columbia Plateaus 

Among the striking physiographic features of the Columbia River 
region are the coulees that occur in Washington from Patterson to Connell 
east of the Cascades. Many of them are scores of miles in length and 
of notable width and depth. They are dry or contain only small streams 
in spite of their great size. They have all the topographic qualities of 
river valleys in addition to tributary systems of branching valleys with 
stream-carved bluffs. Some of them represent an earlier period of more 
abundant rainfall during which wide, flat-bottomed, and cliff-walled can- 
yons were formed. Others are related to the bodily diversion of the 
streams from their preglacial courses and the post-glacial abandonment 
of the temporary courses. 

The largest and most rambling of the coulees is Grand Coulee. It is 
not only of greater interest scenically but its geologic history has been 
unusually interesting. This great canyon was cut by the Columbia 
River at a time when the profound gorge Columbia was temporarily 

1 I. C. Russell, Geology and Water Resources of the Snake River Plains of Idaho, Bull. 
U. S. Geol. Surv. No. 199, 1902, p. 16. 



COLUMBIA PLATEAUS AND BLUE MOUNTAINS 20I 

dammed by a great glacier that came down the Okanogan Valley, filling it 
to a depth of several thousand feet. Upon reaching the Columbia River 
Valley the glacier expanded and spread out over the plateau for about 
35 miles. The displaced Columbia flowed along the eastern face of the 
glacier for two miles below Coulee City, where the bottom of the can- 
yon drops abruptly and where the Columbia River once poured over a 
mighty cataract 400 feet high. The gorge below the cataract extends 
southward for 15 miles. 

The lakes of the plain of the Columbia are situated in the coulees. 
They occupy basins that represent the former irregularities of chan- 
nel bottom, or that have been formed by the irregular distribution of 
wind-blown material. They are elongate in form and often disposed in 
chains. This is the character of Moses Lake, the largest body of water 
in the district. The lakes in the northern part of the Grand Coulee 
occasionally flow to the south at seasons of high water and are therefore 
comparatively fresh and palatable. On the other hand the waters of 
the southern lakes become successively more alkaline, and Soap Lake, 
the most southern, is extremely alkaline. On stormy days it is beaten 
into great masses of white foam on the exposed shore. The substances 
in solution consist essentially of carbonates, sulphates, and bicarbonates 
of soda. 

Stream Terraces 

Later episodes in the history of the Columbia Plateaus are inferred 
from the gravel deposits associated with the streams in the form of 
terraces. They indicate that after the erosion of the deep, rock canyons 
there followed a period during which the streams aggraded their val- 
leys to depths of many feet, — in the case of the Columbia at least 
several hundred feet. Later still, a second period of down-cutting was 
inaugurated in which the streams degraded their channel bottoms, in 
some cases to bedrock. There were temporary halts in the down- 
cutting which are now expressed by the lower terraces.^ In many cases 
the streams have again begun the aggradation of their valley floors.^ 

The canyon walls of the Columbia River, for example, are marked by 
a succession of terraces in part carved out of bedrock and in part com- 
posed of stream-laid gravels. The largest of these terraces is known 
as the "Great Terrace of the Columbia" and is distinguished from its 
neighbors by its great extent and perfection of development. The ter- 
races above the Great Terrace were built by streams along the sides of 

1 F. C. Calkins, Water-Supply Paper U. S. Gaol. Surv. No. ii8, 1905, p. 43. 
» Idem, p. 45. 



202 FOREST PHYSIOGRAPHY 

the Okanogan glacier during the period of its decHne. These terraces 
are less regular than the lower ones and are characterized by more 
numerous deep pits or kettle holes, while the material composing the 
terraces suggests glacial debris slightly modified by water.' On the 
other hand the Great Terrace is of postglacial age and is due to the 
fact that the canyon of the Columbia was once filled with fluviatile de- 
posits from 300 to 500 feet above the bedrock floor and to the level of 
the Great Terrace. The terraces below the Great Terrace simply mark 
halts in the process of dissection in postglacial time of the original gravel 
filling.i 

Gravel plains of large extent were also developed along the interna- 
tional boundary line in the form of low delta deposits and terraces, the 
variety of minor features being due to the interaction of ice and stream 
work. 

Climate, Soil, and Vegetation 

CLIMATE 

The Columbia Plateaus everywhere receive a deficient rainfall, since 
the province is practically surrounded by mountains of notable height 
and continuity. On the west are the Cascades, which so thoroughly 
intercept the rain-bearing westerly winds as to leave even the higher 
eastern slopes of these mountains rather dry and the lower slopes very 
dry. The lower and flatter country to eastward is also very dry and 
in general receives from 8 to 25 inches of rainfall; the lesser amount 
falls on the Great Sage Plains of central Oregon and the low^er Snake 
River Valley, the greater amount being restricted to the higher relief 
features such as the Blue Mountains of northeastern Oregon and other 
ranges of lesser height. Sufficient rain falls upon these mountains to sup- 
port a forest growth, but the amount in even the most favored situations 
is nowhere large, and none of the forests is dense. The Blue Mountains 
shut in the plain of the Columbia on the south in eastern Washington, 
just as the Owyhee, Goose Creek, and Bear River ranges shut in 
the Snake River Valley on the south. On the north the plain of the 
Columbia is sheltered from cold winter winds by the Okanogan and 
Columbia ranges, on the east by the Coeur d'Alene; the valley of the 
Snake is similarly sheltered in these directions by the great mountain 
mass of the Clearwater and Salmon River mountains of central Idaho 
and the Bitterroot Mountains on the Idaho-Montana line. In both 
cases, however, the bordering ranges exact their toll of rainfall and leave 
the plains relatively dry. In eastern Washington the rainfall increases 

1 Smith and Calkins, A Geological Reconnaissance Across the Cascade Range near the 
49th Parallel, Bull. U. S. Geol. Surv. No. 235, 1904, pp. 38-41. 



COLUMBIA PLATEAUS AND BLUE MOUNTAINS 203 

somewhat because of increasing elevation, though this increase should 
not be confounded with increases on the mountainous elevations farther 
east. It is sufficient over a restricted tract to make possible farmirig 
without irrigation. 

The partly enclosed character of the Columbia region causes its mean 
annual temperature to be much higher than one would expect from its 
latitude and altitude. Very low winter temperatures prevail, however, 
in the mountain tracts, especially in the mountainous area of central 
Idaho, with the result that the snowy precipitation is heavy and the 
snow melts slowly and remains late the following spring. The effect is to 
give the streams draining across the bordering valleys and plains access 
to a natural storage of precipitation of the greatest value in maintain- 
ing a proper flow. Since forest trees normally require only about 100 
days a year free from snow, the slow melting in late spring of the heavy 
snowfall of winter greatly increases the value of the total yearly precip- 
itation available to the forests of the region without interfering with 
their growth. In the Columbia region grazing must always constitute 
the most important industry from the standpoint of the extent of terri- 
tory involved. Irrigation by means of mountain streams may, however, 
become the most important industry as regards the value of the products. 

SOILS 

The desert quality of the climate of the region is emphasized by the 
presence of an extensive layer of pumiceous gravel, sand, and dust. It 
covers tracks aggregating several thousand square miles in extent. 
It is particularly abundant east of the Cascades, and also extends west- 
ward over portions of the mountains and down their slopes for twenty 
miles or more. Both the Great Sandy Desert (see Fig. 52) and the coun- 
try west of it display this feature. In many places the layer of volcanic 
dust is fully 50 feet thick and a maximum thickness of 70 feet has been 
recorded.^ It is extremely porous, permits the quick descent of the 
ground water, and invariably accentuates the dryness of the climate east 
of the Cascades. 

On the great plain of the Columbia in eastern Washington and in 
many other localities the soils have been described as residual, as having 
been formed in place by the decay of the basalt. Calkins shows con- 
clusively,^ however, that in many portions of Washington the soils 

1 I. C. Russell, Geology and Water Resources of Central Oregon, Bull. U. S. Geol. Surv. 
No. 252, 190S, p. 16. 

2 F. C. Calkins, Geology and Water Resources of a Portion of East-Central Washington, 
Water-Supply Paper U. S. Geol. Surv. No. iiS, 1905, p. 45. 



204 



FOREST PHYSIOGRAPHY 



have been formed by wind action. The conclusion is based upon the 
facts that there is an absence of lamination in the soil, that it is extremely 
fine in texture, that there is a remarkably sharp definition between the 
soil and basalt, and that comparative chemical analyses indicate soils 
not of the character naturally to be expected from the decomposition 
of basalt in this climatic province. The principal source of the material 
appears to be the soft sedimentary beds (EUenberg formation) in the 
southwestern portion of the Columbia plains. 

The soils are fine loams, very light, open, and friable, with a light, 
tawny, brown color. The thickness of the soils varies according to 
location from 25 to 50 feet, the greatest thickness being on the brows 
of slopes where there is the most favorable opportunity for the accumu- 
lation of wind-blown material. 

The character of the so-called "dust soils" of Oregon and Washington 
is typically represented by the following analysis. They are light, dry 
soils raised into clouds under natural conditions at the slightest wind 
and probably originated entirely through wind action akin to that which 
resulted in the formation of loess. ^ 



CHEMICAL ANALYSES OF DUST SOILS^ 



Constituents 



Atathnam Prairie, 

Yakima County, 

Washington 



Rattlesnake 

Creek, 

Kittitas County, 

Washington 



III 



Plateau on 

Willow Creek, 

Morrow County, 

Oregon 



Insoluble matter 

Soluble silica 

Potash (K2O) 

Soda (NaaO) 

Lime (CaO) 

Magnesia (MgO) 

Brown oxide of manganese (MnsO^ 

Peroxide of iron (Fe203) 

Alumina (AI2O3) 

Phosphoric acid (P2O6) 

Sulphuric acid (SO3) 

Water and organic matter 

Total 

Humus 

Hygroscopic moisture 



71.67 

S-ii 
1.07 

0.3s 
2.00 

1-34 
0.04 
6.88 
7.91 
0.13 
0.02 
2.82 



76.78 



78.3, 



80.53 



2.35 



% 

f 81.51 
2.30) 

0.89 

0.05 

1-37 

1.08 

0.06 

5-63 

6.02 

0.18 

0.03 

2-55 



99-33% 
4. 10 
4.98 



99-90% 



3.20 



99-35% 
0.44 
4.92 



The most extensive and uniform soil types of the Columbia Plateaus 
consist of residual materials overlying extensive basaltic lava plains. In 

1 G. P. Merrill, Rocks, Rock-weathering and Soils, 1896, p. 345. 

2 Bull. U. S. Weather Bureau, No. 3, 1892. 



COLUMBIA PLATEAUS AND BLUE MOUNTAINS 205 

some cases the soils have been derived from granitic rocks or from ancient 
lacustrine sediments or extensive lake beds now more or less modified by 
erosion or aeolian agencies. The margins of the lacustrine or residual 
deposits are covered by sloping plains and fans of colluvial wash from the 
adjacent mountain borders, while in the vicinity of the larger streams, 
which have carved and terraced the lacustrine beds and residual soils, 
are recent alluvial stream sediments derived from reworked materials 
of the lake beds or from the weathered products of the mountains. 
Soils of this type constitute a large portion of the great grain-producing 
lands of the Northwest. Everywhere the soils are treeless or sparsely 
timbered, except in the vicinity of streams. 

The higher lying areas are often rough and hilly, marked by rock 
outcrop, bowlders, or morainic debris, and deeply cut by stream chan- 
nels. Their soils " are generally of dark color, and are underlain by 
sticky subsoils of light-gray or yellow color. The soils and subsoils 
are generally gravelly, the gravel varying from fine angular chips to 
large, well-rounded or angular blocks and cobbles. The soils are dry 
farmed to grains or, when not occupying too high a position, are irri- 
gated and devoted to grains, alfalfa, clover, and fruits." ^ 

Recent flood-plain deposits are underlain by beds of gravel and 
cobbles, usually from a few inches to a few feet thick, sometimes 
partially cemented by lime. They are often marked by shallow beds 
or channels of meandering streams, and are frequently timbered or cov- 
ered with willow or brush thickets in the vicinity of streams. They 
usually occur as small irregular to extensive areas, often subject to over- 
flow. The flood-plain soils are generally rich in organic matter and of 
a mucky consistency, except in the lighter, higher lying members, and 
sometimes contain alkali.^ The basalt of the Columbia plain weathers 
easily and has been decomposed to form a rich residual soil which mantles 
the surface and gives its slopes characteristic soft, rounded, flowing 
outlines.' 

The greatest difficulty in the utilization of the water of the Snake 
and the Columbia arises from the fact that large stretches of these rivers 
occur at great depths below the general level of the country. The 
Columbia flows in a canyon with fairly abrupt walls sunk from 100 to 
1000 feet below the broad stretches east of it in Washington. Further- 
more, its gradient is much lower than that of much of the land along 

1 Soil Survey Field Book, U. S. Bur. of Soils, igo6. 

2 Idem. 

' I. C. Russell, A Reconnaissance in Southeastern Washington, Water-Supply Paper U. S. 
Geol. Surv. No. 4, 1897. 



2o6 FOREST PHYSIOGRAPHY 

it and the application of its water to the soil is therefore exceedingly 
difificult. The most important streams, from the standpoint of irriga- 
tion, are those which drain the eastern flanks of the Cascades, as the 
Yakima, Kittitas, and others.^ 

VEGETATION 

Throughout southern Idaho and over the greater portion of Oregon 
east of the Cascade Mountains the sage-bush is the characteristic 
plant. It is nowhere absent save on the barren mud plains left by the 
drying up of the ephemeral lakes, or upon the summits of the moun- 
tains. While not so plentiful as the sage-bush the bunch grass is dis- 
persed almost as widely. The fresh-water ponds of the coulee bottoms 
are bordered by tule, while the meadows in the same situations are 
covered with wild grasses. The small streams are fringed with a 
scattered growth of willow, birch, and wild cherry.^ With increase in 
elevation the juniper makes its appearance, and beyond the lower limit 
of the juniper are thickets and groves of mountain mahogany. At still 
higher elevations, yet within the range of the mountain mahogany, the 
pine appears and reaches up to an elevation of 8000 to 10,000 feet. 
However in only two areas in the whole southeastern quarter of Oregon 
do forests of any considerable extent occur. Castle Rock in Malheur 
County, Oregon, is on the border of an extensive forest of pines, as well 
as juniper, mountain mahogany, and many other trees, and a splendid 
forest exists on the mountains northwest of Harney and Burns in which 
the Silvies River has its sources. 

Above 7500 feet the peaks of the Seven Devils and of the Eagle 
Creek range in Oregon are flecked with snowdrifts and scored by 
rock slides and a forest cover is wanting. A forest zone consisting of 
black pine above and yellow pine below extends from 4000 feet to 7500 
feet. Below 4000 feet the canyon walls of the Snake are again almost 
bare.^ The bottom of the canyon is at an elevation of about 1600 feet; 
snow rarely falls in it, and the rainfall is almost equally scant, so that 
only desert types of vegetation grow upon it. 

The occurrence of forests in the region depends upon many factors, 
chief of which is the moisture supply. The whole tract is extremely 
dry and one must always ascend to a considerable elevation to find a 
forest growth. The lower edge of the forest growth is called the "dry 

1 F. C. Calkins, Water-Supply Paper U. S. Geol. Surv. No. ii8, 1905, p. 18. 

2 Idem, p. 22. 

' W. Lindgren, The Gold and Silver Veins of Silver City, De Lamar, and Other Mining 
Districts in Idaho, 20th Ann. Rept. U. S. Geol. Surv., 1898-1899, pt. 3, 1899, p. 92. 



COLUMBIA PLATEAUS AND BLUE MOUNTAINS 207 

timber line." On ascending the forest-clothed mountains one reaches 
also an upper limit of tree growth, the "cold timber line," beyond 
which only shrubs, stunted trees, and alpine flowers exist. If the 
aridity is intense the dry timber line will be high and the forest belt cor- 
respondingly narrow; if the aridity is not extreme the forest belt will be 
wide. In many cases the aridity elevates the dry timber line until it 
coincides with the cold timber line and no forest exists in such cases 
even though the mountains have a great elevation. It is for this reason 
the prominent Stein Mountains of southeastern Oregon have no forests. 
It may readily be seen that mountains which project above the dry tim- 
ber line but which do not reach the cold timber line have forest-clothed 
summits, while those whose summits reach to elevations below the dry 
timber line or above the cold timber line are bare.^ On the Cascade 
Mountains in central Oregon the cold timber line has an elevation of 
about 8000 feet, while the dry timber line, marked by the cessation of 
the yellow pine, may be taken at approximately 4000 feet. 

In the use of the vegetation the scarcity of surface water upon areas 
underlain by volcanic ash is apparent in two main ways. Water is not 
available for fighting forest fires even though there is sufi&cient ground 
water to support a forest growth ; and over large areas there is an excel- 
lent growth of grass untouched by sheep or cattle because of the absence 
of drinking water in the form of springs or running streams. The ash 
cover is a rapid absorbent and rain water that falls upon it almost 
immediately becomes ground water. A heavy restriction is thus laid 
upon the use of the land and its products, though at least one bene- 
ficial result follows — the larger streams of the region are kept in more 
even flow. 

BLUE MOUNTAINS 

The Blue Mountains of northeastern Oregon have received far less 
attention than they deserve from physiographers and geologists as well 
as from foresters. They lie in a very interesting position midway be- 
tween the mountain complex of central Idaho and the Cascades, and 
are a projecting spur of the great crust-block composed of the Lost 
River, Bitterroot, Clearwater, and Salmon River mountains. While 
they extend well across the basin and plateau region between the Rocky 
Mountain system and the Pacific Mountains, they do not connect 
directly with the Sierra Nevada and the Cascades. From the stand- 
point of rainfall and forests the Blue Mountains (8500 feet) are the 

1 I. C. Russell, Notes on the Geology of Southwestern Idaho and Southeastern Oregon, 
Bull. U. S. Geol. Surv. No. 217, 1903, p. 11. 



2o8 FOREST PHYSIOGRAPHY 

most important relief feature in the entire region between the Cas- 
cades and the Rockies since they cause a local rainfall (15 to 25 inches) 
that waters the fertile valley flats and a belt of peripheral country of 
considerable extent. 

Topographically the Blue Mountains consist of all that group of 
complex ranges that constitute the country between the Deschutes 
Valley on the west, the Malheur and Harney deserts on the south, and 
the Snake and Columbia rivers to the east and north. Within the 
mountain knot thus outlined are a number of ranges with such specific 
qualities that they have received separate designations. Conspicuous 
among these are the Eagle Creek Mountains, the Elkhorn Range, the 
Greenhorn Ridge, the Strawberry Range, and others. The mountain 
group thus defined stands out prominently above the surrounding plain, 
which lies from 4000 to 6000 feet above sea level. The highest peaks of 
the Blue Mountains rise to heights over 9000 feet above the sea and 
many exceed 8000 feet. 

The geologic features necessary to an understanding of the physiog- 
raphy of these mountains may be briefly stated. The sedimentary rocks 
of which they are chiefly composed have been not only extensively and 
rather generally folded but also quite thoroughly intruded by grano- 
diorite, diorite, gabbro, and peridotites. The intrusions were accom- 
panied by uplift, — the net result of folding, intrusion, and uplift being 
the formation (Jurassic and early Cretaceous) of a mountain knot of 
impressive height. Upon this complex mass erosion produced profound 
effects, stripping off a great mass of material and laying bare the heart 
of the mountains. While they were thus deeply dissected they were 
never reduced to an old-age condition; erosion was carried only so far as 
to make them very rugged; so that were one to take away the lava flows 
about the Blue Mountains they would stand out as imposing heights. 
Lava flows (Miocene) derived from numberless fissures on the flanks 
of the mountains were then spread far and wide over the surrounding 
country, burying the older topography, subduing the relief, and sepa- 
rating the Blue Mountains from the Rockies, causing them to stand out 
as islands in a basaltic sea. The first flows were rhyolites and andesites, 
the later flows were basalts in increasing volume. 

The effects of the great lava flows were not confined to topographic 
and drainage changes in the valleys of the Columbia and the Snake, 
but were exhibited as well in the marginal tracts of the Blue Mountains. 
The effects are all the more striking because of the former well-devel- 
oped character of the drainage. The present river courses and the 
sediment-filled upper basins that are the products of volcanic flows are 



COLUMBIA PLATEAUS AND BLUE MOUNTAINS 209 

among the most difficult physiographic problems of the region. The 
lower parts of the watercourses became filled with basalt, damming the 
headwaters and creating lakes that were afterwards drained to a large 
extent by the downcutting at their outlets, thus producing physiographic 
effects of puzzling complexity.^ 

The precipitation of the Blue Mountains is heavy enough to produce 
a forest of yellow pine which shades off to mountain mahogany, juniper, 
and other types, in lower and therefore drier situations. The greater 
part of the tree cover consists of an open woodland growth since even the 
best watered areas receive a limited rainfall and snowfall. Small summit 
areas on the higher mountains, such as the Strawberry Range, Fig. 52, 
and the Powder River Range north of it, are without a tree cover since 
their elevations exceed that of the cold timber line, about 8000 feet. 
The alluvium-filled mountain basins, noted above, and the forest cover 
combine to keep the streams in more even flow than would otherwise 
be the case, thus making possible an important amount of agriculture 
in the lower irrigated valleys. The result is a fringe of population about 
the flanks of the mountains with finger-like extensions down the major 
depressions. 

' W. Lindgren, The Gold Belt of the Blue Mountains, 22d Ann. Rept. U. S. Geol. Surv., 
pt. 2, pp. 574, S7S, 594, 597, et al. 



^ CHAPTER XIV 

GREAT BASIN 

Arid Region Characteristics; Hydrographic Features 

In spite of the prevailingly arid character of the, western half of the 
United States its streams are in large part through-flowing, a feature due 
chiefly to the loftiness and position with respect to rain-bearing winds 
of the mountain groups and ranges in which their sources lie. The 
Columbia and the Colorado, for example, although they lose a part of 
their water by evaporation and absorption, yet maintain a considerable 
volume up to the point of discharge; and in other similar cases the 
large headwater contributions maintain a perennial flow. Therefore, in 
respect of drainage a relatively small portion of the arid West has the 
characteristics usually associated with pronounced aridity — interior 
basins, large streams which disappear on piedmont slopes, and salt 
lakes such as those that characterize the deserts of Asia, or the Sahara 
desert in Africa. 

Two large physiographic provinces of the United States are excep- 
tions to this general rule — the Great Basin and the basin of the Lower 
Colorado. Of the two the Great Basin has the more reniarkable de- 
velopment of those drainage features that are an index of extreme 
aridity. The drainage of the entire Great Basin is of the interior-basin 
variety, no part of the water that falls within it reaching the ocean 
by surface drainage. Everywhere the streams descend from the better- 
watered mountain ranges to waste-floored forelands, where a large part 
of their water — sometimes the whole — is lost by evaporation and 
absorption. Such excess of water as locally fails to be absorbed by 
the porous sands and gravels of the piedmont regions is gathered upon 
the floors of depressions between mountain ranges in the form of salt 
lakes or lakes that are strongly alkaline. 

Salt Lakes of the Great Basin 

Chief among the salt lakes of the Great Basin are Great Salt Lake, 
Lake Humboldt, Carson Lake, and the group of saline lakes that occupy 
the Sage Plains of central Oregon, Fig. 52. Some of the lakes of the Great 



GREAT BASIN 



211 




n,rf„.„„i„. p, ,.,„ PREStNT DRMNAGE ARF \S OF THE L\HON TAN REOION , . „ ^ 

Hidro§ra^ihn, bouiidani,s>^— -w ^ LaJiotiUtii Death 



Fig- 53- — Illustrates the small size and independent character of the drainage systems of the Great Basin 
region. (Russell, U. S. Geol. Surv.) 



212 FOREST PHYSIOGRAPHY 

Basin are composed of very dense brine of common salt, sodium sulphate, 
and other substances. It has been estimated that Great Salt Lake alone 
contains 400,000,000 tons of common salt.^ Not all the lakes tributary 
to or in the Great Basin are of this character however. ■ Some of 
them consist of pure wholesome water, such as Utah Lake, Bear Lake, 
and Lake Tahoe on the western edge of the Great Basin and near the 
forested heights of the Sierra Nevada. Wherever a constant outlet is 
assured, the lakes consist of sweet water, but an interrupted outflow is 
always indicated by an increase of salinity, and the absence of an out- 
flow results in the concentration of chemical salt to such an extent as to 
result in dense brines. 

Another important feature of many lakes of the Great Basin is their 
ephemeral character. In a large number of instances lakes exist on 
the basin floors only during periods of high water in the feeding 
rivers; in dry seasons such lakes evaporate and expose broad flat 
expanses of mud which soon become dry and sun-cracked and present 
on the whole a monotonous and forbidding appearance. These are 
called playas and are desert features as characteristic as sand dunes or 
lost rivers. 

The rapid manner in which some playas are transformed into shallow 
lakes is almost incredible to one unacquainted with rainfall conditions 
in desert regions. A single storm will sometimes form a shallow lake 
whose waters are spread far and wide over a basin floor. The disap- 
pearance of such a lake may be almost as rapid as its formation, for 
the mud cracks, at least for a time, allow easy passage of the water 
to lower levels, and with the high temperature and clear skies charac- 
teristic of arid regions, surface evaporation is rapid, and often within a 
few days, sometimes even in a few hours, after the rain has ceased, the 
smaller lakes have disappeared. 

It is easily seen that the sudden appearance and disappearance of 
lakes in the Great Basin region are to a large extent functioned by the 
flatness of the basin floors on which the waters rest. Sudden and great 
differences in topographic level are not characteristic of regions whose 
surface forms are products of alluviation. The graded and gentle waste 
slopes of piedmont forelands and aggrading basin floors are surfaces of 
such slight relief that waters which come to rest upon them may be 
spread over great areas and yet nowhere be of great depth. Great Salt 
Lake is an illustration in point. Its average depth is from 15 to 18 
feet; its maximum depth is less than 50 feet. Its area in 1850 was 
1750 square miles, but by 1869 its volume had increased to 2170 

1 I. C. Russell, North America, 1904, p. 142. 



■ GREAT BASIN 213 

square miles.^ From 1900 to 1904 it was feared it would disappear 
entirely and its bed become a salt desert. Since that time the level has 
risen to such an extent that large engineering works, like the Lucin 
cut-off of the Southern Pacific and the roadbed of the Western Pacific 
are endangered and may have to be abandoned. These changes are 
mainly in response to changes of rainfall, 19 10 having been abnormally 
wet.^ The changes that have taken place in the past half century are 
to be regarded as changes that may be repeated at any time in the 
future. 

The rate of supply of water to the lake is constantly undergoing 
changes in sympathetic response to changes in precipitation in the 
drainage basin. Likewise, the rate of evaporation at the lake surface is 
subject to considerable fluctuation. A third variable factor is the rate 
at which water is diverted from tributary streams for irrigation pur- 
poses. All of the natural changes are subject to periodic fluctuations. 
Climatologic studies have shown that rather definite changes are char- 
acteristic of the climatic elements in all portions of the earth. These 
changes are cyclic in character and occur in periods of 11 and 35 years 
and undoubtedly in even longer periods of a hundred, several hundred, 
and even many thousands of years. The effects of the cyclic return of 
wetter conditions have been noted in the case of many\akes of humid 
regions and in their discharging streams; but the maximum effects of 
such climatic changes are felt in regions in which the drainage is of the 
interior-basin variety. The water of an interior basin must rise in re- 
sponse to wetter conditions until evaporation from the expanded sur- 
face just equals the rate of supply. The amount of expansion would 
represent, roughly, the increase of rainfall. If the changes from wet to 
dry and from dry to wet are not only cyclic but also progressive in one 
direction, as appears to have been the case at least during and since the 
glacial period, the repeated rise and fall of the lake surface by large 
amounts would be recorded in the form of shore features of familiar 
kinds. Thus there are small changes of lake level that affect all lakes in 
all climates ; also changes of greater amplitude and of far greater physio- 
graphic importance, that may be designated as geologic. Such changes 
are best recorded in the basins of desert regions, for these are, on the 
whole, without outlet, and the surplus waters are confined and must 
faithfully record upon their margins the manner in which the changes 
occur. 

1 G. K. Gilbert, Lake Bonneville, Mon. U. S. Geol. Surv, vol. i, 1890. 

2 Ebauch and Macfarlane, Comparative Analyses of Water from the Great Salt Lake, 
Science, n. s., vol. 32, 1910, p. 568. 



214 FOREST PHYSIOGRAPHY 

Since the Great Basin is the only large physiographic province in the 
United States in which interior-basin drainage predominates, it fol- 
lows that the clearest drainage records of climatic change are to be 
found there. During the glacial period a wetter chmate prevailed in 
extra-glacial regions such as the Great Basin, and each lake in this 
province expanded until the rate of evaporation or evaporation and 
discharge just equaled the supply. The two largest of these lakes 
were in Utah and Nevada. The ancient lake that once existed in 
Utah has been called Lake Bonneville; its counterpart in Nevada is 
known as Lake Lahonton. Lake Bonneville has all but disappeared, its 
descendant being Great Salt Lake; and the discontinuous water bodies 
called Lake Lahonton have shrunk to such an extent that the lowest 
parts of the various basins are to-day occupied by a few salt- and 
brackish-water lakes such as Carson Lake, Humboldt Lake, etc. Dur- 
ing its maximum development Lake Lahonton contained salt water, 
as its shrunken remnants do to-day, though it was undoubtedly less salt 
than they; on the other hand, Lake Bonneville was fresh or only 
slightly alkaline when it stood at its highest level, for it rose so high as 
to discharge for a time over the col on the divide between its basin and 
the Snake River Valley. 

About the borders of the basin of Great Salt Lake may be seen shore 
features associated with the ancient lake levels and still in an almost 
perfect state of preservation. Upon the surrounding slopes and up to 
elevations of 1500 feet above the surface of Great Salt Lake are well- 
defined deltas, bars, beaches, spits, capes, cliffed promontories, and 
bottom deposits, all formed by or associated with the ancient lakes 
whose waters once stood at these high levels.^ 

Some of the most interesting and important lake features of the Great 
Basin are associated with the lakes of southern Oregon. For example, 
the water bodies in Lake County, southern Oregon, are all shallow. 
None exceeds 25 feet in depth. The size of these shallow water bodies 
depends on the seasonal rainfall, and changes in size are characteristic 
features in the absence of an outlet to the sea which might permit the 
maintenance of a more or less constant level, the level of the point of 
discharge. Important changes in the outline of some of these lakes 
have taken place since the settlement of the country. 

In the early days of Lake View the town was on the edge of Goose Lake, but it is now six 
miles from it. In 1869 the lake overflowed for a short time southward into Pitt River. In 
1881 it also overflowed for two hours during a severe gale from the north. 2 The fluctuation in 

' G. K. Gilbert, Lake Bonneville, Mon. U. S. Geol. Surv., vol. i, 1890; I. C. Russell, Geo- 
logical History of Lake Lahonton, Mon. U. S. Geol. Surv., vol. 11, 1885. 
2 I. c. Russell, 4th Ann. Rept. U. S. Geol. Surv., 1884, pp. 456-457. 



GREAT BASIN 



215 



'aT ^ 




3 w 



2l6 FOREST PHYSIOGRAPHY 

the level of Goose Lake is also marked by the fact that in the early emigrant days the trail 
crossed Goose Lake Valley at a point where now the floor of the valley is under several feet 
of water.i The fluctuations in lake level have brought about a certain amount of htigation in 
relation to lands in the valley of Warner Lake, the decision turning upon the question whether 
some 4000 or 5000 acres now dry was swamp land or part of the bed of the lake at .the time of 
the passage of the Swamp Land Act of i860. After the exceptionally dry season of 1887-88, 
Silver Lake dried up, its bed was cultivated by farmers and one season's crops were gathered 
before the lake again occupied its old floor.^ 

The degree of alkalinity of the lakes of southern Oregon may be ap- 
preciated by comparison with the average alkaline content of the fresh- 
water lakes of North America as given by Russell,^ who notes that the 
amount of alkaline material in the fresh-water lakes of this continent 
is between 15 and 18 parts in 100,000. The water of Summer Lake, 
Oregon, on the other hand, has 500 or more parts of salt (sulphate of 
soda, carbonate of soda, and bicarbonate of soda) in 100,060.^ The 
practical bearing of these facts may be appreciated when it is known 
that the limit of alkalinity for domestic or irrigation purposes is about 
400 parts to 100,000, although this limit depends largely on the character 
of the salt in each particular instance. The water of Lake Albert, south- 
ern Oregon, has a content of 3.9% of salt, showing that the water is 
more strongly impregnated than ocean water, which contains about 
3.5 % of mineral salt.^ 

Rivers of the Great Basin; Precipitation 

The chief rivers of the Great Basin receive their principal supply of 
water not from rainfall in their middle or lower courses but from melt- 
ing snows in the mountains, as on the eastern and western borders of 
the basin. The stream discharge of the region is characteristic, the 
maximum occurring in the late spring or early summer, with a decrease 
of flow during the summer and a minimum during the winter months. 
The streams receive little or no additions after leaving the mountains, 
and diminish in size and often cease to flow at the surface.^ The streams 
which discharge eastward from the Sierra Nevada, such as the Carson and 
the Truckee, have an immense run-off during the late spring, although 
the snows accumulate to a great depth in their thickly forested head- 

1 G. A. Waring, Geology and Water Resources of a Portion of South-Central Oregon, Water- 
Supply Paper U. S. Geol. Surv. No. 220, 1908, p. 12. 

- Idem, p. 12. 

' I. C. Russell, Lakes of North America, 1897, p. 55. 

* G. A. Waring, Geology and Water Resources of a Portion of South-Central Oregon, Water- 
Supply Paper U. S. Geol. Surv. No. 220, 1908, p. 14. 

5 Idem, p. 13. 

5 La Rue and Henshaw, Surface Water Supply of the United States, 1907-08, pt. 10, The 
Great Basin, Water-Supply Paper U. S. Geol. Surv. N©. 250, 1910, p. 28. 



GREAT BASIN 21 7 

water regions and a considerable quantity is stored in natural lakes 
which supply water gradually to the streams into which they discharge. ^ 

The streams that descend from the basin ranges are variable as to 
length and discharge, the latter feature depending ultimately upon the 
great variations in the height of the mountains (Fig. 55) with which the 
rainfall and snowfall are inevitably associated. Most of them disappear 
in the loose material of piedmont slopes, some of them discharge into 
lakes, all of them are subject to considerable variation in volume. 
These variations are immediately related to the forest and soil cover of 
the mountains in which the sources lie and to the rapid melting of the 
winter snows provided the mountains are of sufficient height to receive 
their precipitation in this form during the winter months. Only a few 
of the highest ranges were ever glaciated, hence few lakes occur in the 
regions of snowy precipitation, and natural storage of mountain waters 
is markedly absent. Those streams that are supplied by melting snows 
have great changes in volume from season to season, especially if the 
supply from springs is exceptionally deficient.- Thus the Humboldt 
River derives its supply from the melting of snows in headwater regions, 
and the run-off during the spring and summer months is very heavy; 
but as soon as the snow is gone the rivers are left practically without a 
source of supply and their channels gradually become dry. 

Few better illustrations can be found of a stream not subject to 
excessive changes of volume and yet without forests or extensive 
meadows than Bear River, which drains the northern slope of the Uinta 
Mountains and discharges its waters into Great Salt Lake. The basin 
contains no marshes and but few small lakes near the head of the river, 
but the greater part of the precipitation is in the form of snow and the 
chief sources of supply are from melting snow and from numerous small 
springs. The latter form so steady a supply that after the annual high- 
water period during May and June the stream although diminished in 
volume does not cease to flow.^ 

Special Topographic Features 

Having no outlet to the sea, the streams of the Great Basin sink into 
the alluvium of the basin slopes and floors or evaporate from the sur- 
faces of Salinas and salt lakes. The surface evaporation of the drainage 
waters also halts the waste which the drainage water carries and it 

1 La Rue and Henshaw, Surface Water Supply of the United States, 1907-08, pt. 10, The 
Great Basin, Water-Supply Paper U. S. Geol. Surv. No. 250, 1910, p. 100. 

2 Idem, p. 56. 

3 La Rue and Henshaw, Surface Water Supply of the United States, pt. 10, 1907-08, The 
Great Basin, Water-Supply Paper U. S. Geol. Surv. No. 250, 1910, p. 29. 



2l8 FOREST PHYSIOGRAPHY 

therefore accumulates upon the land and tends to aggrade it. The dis- 
position of the waste brought down by desert streams to lower levels is 
thus of special interest. Each basin floor becomes a local base level if 
there is no outlet to a lower basin. In the case of normal topographic 
development the surface of the land, though it may be built up tempo- 
rarily, tends ultimately to be worn down to base level, which is almost sea 
level. In the development of the topography of a desert tract with 
interior-basin drainage, like the Great Basin, the elevations are worn 
down but the depressions are built up. The plane of reference, the com- 
mon plane to which these forces will ultimately br^ng both depressions 
and elevations, is then not sea level but some higher level of indeter- 
minate position. When this level has been attained further degrada- 
tion of the surface will be chiefly through the exportation of dust by 
the wind to extra-desert regions. The drainage systems, at first inde- 
pendent and local, will become more and more interdependent and 
general, as one basin after another becomes filled or captured and enters 
into tributary relations with some lower neighboring depression. When 
the heights have been reduced and the basins all filled to a common 
level the rainfall is lessened by the decrease of relief and the streams 
will become enfeebled and disorganized or over large tracts cease to flow 
altogether. 

The Great Basin streams are still in the early stages of basin filling. 
The region was deformed so recently (Miocene) that the topographic 
forms produced by the last deformation are still of mountainous pro- 
portions and the basins are only partly filled with land waste. Whether 
an ultimate level will be reached will depend (i) on the stability of the 
present climate: at one time (Pleistocene) a Great Basin lake (Bonne- 
ville) overflowed to the sea because of a wetter climate, and the same 
occurrence may be repeated. (2) It will also depend on crustal stabiUty : 
some crustal movements have occurred in late geologic and even in his- 
toric time; if they are repeated and extensive they may offset the tend- 
ency toward leveling on the part of the streams. 

Basin Ranges 

The most important topographic elements of the Great Basin are the 
roughly parallel mountain ranges that cross it from south to north and 
that diversify its surface to a greater degree in Nevada than elsewhere. 
The mountains are long and narrow and frequently have sharp crests 
with steep slopes on one side and relatively gentle slopes on the other. 
The mountain ranges of the Great Basin are explained by block faulting. 
In general each range may be considered as the upturned edge of a 



GREAT BASIN 



219 



?/ 



;4{ 



JH: 



o 



111.' 



2 c^ 

^ .s 






S c 
S E! 



2 20 



FOREST PHYSIOGRAPHY 



block of the earth's crust, the faulted edge of the block forming a steep 
scarp, the tilted back of the block forming a long and relatively gentle 
declivity that merges imperceptibly into the bordering plain. 

In some instances the rocks of the basin ranges appear to have been 
so complexly faulted that the relief has a peculiarly irregular quality 
with an absence of parallel ridges and valleys such as characterize the 




Fig- 56. — Plan of the principal faults in the Bullfrog district, Nevada. (Emmons, U. S. Gaol. Surv.) 

greater number of the basin ranges. The result has been described as a 
fault mosaic. The complexity of the main fault systems in the Bullfrog 
district, Nev., is indicated in plan in Fig. 56; the vertical displacements 
are shown in Fig. 57. Extensive mining development in Nevada in 
recent years has led to a much more detailed study of actual faults 




Horizontal Scale 

Fig. 57. — Diagram illustrating fault-block displacements in the Bullfrog district, Nevada. 
(Emmons, U. S. Geol. Surv.) 

than has heretofore been possible and has removed from the realm 
theory to that of well-determined fact the question of the existence 
faults that affect the topography. ^ 



GEOLOGIC DATA 

The structure and geologic history of the Basin Ranges are so di- 
rectly related to the physiographic features of the Great Basin that we 

1 In this connection see the paper by W. H. Emmons, A Reconnaissance of Some Mining 
Camps in Central Nevada, Bull. U. S. Geol. Surv. No. 408, 1910, pp. 76-81 et al. 



GREAT BASIN 221 

may well consider for a moment the later geologic events of the region 
in so far as they serve as a guide to the interpretation of the topographic 
forms. 

The internal structures of the Basin Ranges indicate an early period 
of mountain making in which were formed anticlines and synclines 
whose surface expression was probably not markedly unlike that of the 
Appalachian Mountains of to-day. These beginnings of physiographic 
history took place in the Jurassic period and resulted from the extensive 
folding to which the region was subjected at that time and from its 
gradual uplift above the sea. It is inferred from the internal structures 
of the ranges that these early deformations produced mountains of great 
size and height.^ 

The second period of folding (post- Jurassic) took place almost 
entirely on north-south lines or on lines very closely approximating 
this direction. East-w^est lines of folding are extremely rare, and the 
ranges resulting from such folding were neither long nor important. It 
should be carefully noted that the axes of folding trend somewhat more 
east of north than the ridge lines of the present ranges. The formation 
of these early mountain ranges w^as followed by a long period of erosion 
and the development of a topography of very low relief. 

The next important geologic event was the beginning of crustal warp- 
ing and the production of fresh-water lakes in considerable numbers 
and of large size. During the period of crustal warping explosive erup- 
tions took place from a number of volcanic centers, and rhyolitic 
outpourings covered large tracts of land. Great faults were then de- 
veloped and a period of active differential elevation inaugurated. It 
was the differential movement of large crust blocks which produced the 
present mountain ranges and broad intermontane basins. Adjacent 
blocks rose or sank as units, though they did not move as absolutely 
rigid units, for there is evidence of internal deformations of both folding 
and warping on a limited scale. The result of the differential move- 
ments of crust blocks was the formation of the Great Basin as an 
interior basin, the formation of mountain ranges by block faulting, and 
the development of intermontane valleys or great structural troughs 
whose broad characters do not rest upon stream erosion but upon 
faulting and stream aggradation. Since the period of principal faulting 
dissection has progressed to the point where alluvial fans and cones of 
great size have been formed. 

1 G. D. Lauderback, Basin Range Structure of the Humboldt Region, Bull. Geol. Soc. 
Am., vol. 15, 1904, p. 336. 



222 FOREST PHYSIOGRAPHY 

VARIATION IN TOPOGRAPHIC DEVELOPMENT 

The Basin Ranges were not all formed at the same time nor 
of the same material; they therefore possess distinctly variable topo- 
graphic qualities. In the northwestern corner of the basin (southeastern 
Oregon) the ridges appear to be of very recent origin, and their forms have 
been but slightly changed from the original outlines of the tilted blocks. 

Their youthful condition is indicated by the remarkably straight and 
regular character of their frontal scarps and crest lines and by the small 
amount of dissection which they have suffered. Another indication of 
youth is the frequent occurrence of landslides upon their steep faces 
where gradation has not yet produced a surface over which land waste 
is transported in an orderly manner. 

A conspicuous instance is found in the Satas ridge in southern Washington, where the face 
of the upUfted block is so steep that huge landslides have occurred, one of which affected the 
cliS face over a distance of half a mile and at a height of about 2500 feet above the adjacent 
plain. It has a very irregular surface and its margin is circled by a line of hills 200 feet 
high where the material of the plain was pushed up ahead of the slide. 1 

The ranges occupying the central portion of the Great Basin are of 
later origin. Like the ridges of Oregon they appear to have been formed 
by the uplifting and tilting of long narrow blocks, but the blocks are 
larger in Nevada than in Oregon, and the displacements are of greater 
value. Also the dissection of the block mountains of Nevada has pro- 
gressed much further, so that they may be described as maturely dis- 
sected. Each range has one relatively short steep slope and one long 
gentle slope, but the outlines of the original block are scarcely discern- 
ible and the crest lines of the ranges are minutely irregular. 

In southeastern California and southwestern Arizona many of the 
fault-block mountains are in a still older stage of development and indi- 
cate the condition which the young block mountains of Oregon and the 
maturely dissected block mountains of Nevada will ultimately reach. 
They have often been described as presenting the appearance of buried 
mountains, for they are surrounded on all sides by long gentle slopes 
of gravelly waste sometimes overlying a smooth rocky floor as a veneer. 
The original outlines of the blocks have been completely lost; only the 
alignment of the ranges has been maintained. The opposite slopes of 
each range have become nearly equal in both gradient and length. 
There are no pronounced spurs or deep, profound valleys. The moun- 
tains have rather gentle relief and occupy but a small portion of the 
total surface. 

1 W. M. Davis, Physical Geography, iSgg, p. 162. 



GREAT BASIN 



223 



EVIDENCES OF FAULT-BLOCK ORIGIN 

One of the most interesting features concerning the fault-block moun- 
tains of the Great Basin is the physiographic evidence of faulting that is 
there displayed; indeed this class of evidence is of the utmost impor- 
tance in an interpretation of the Basin Ranges, for the prodigious quan- 
tity of waste accumulated about the borders of the mountains and in 
the intermontane basins makes it impossible always to observe the 
structure in detail and to establish by direct observation the fact of 
faulting.^ 




Fig. 58. 



Diagram to illustrate the manner in which the strike of the bed diverges from the mountain 
front in the fault-block mountains of the Great Basin. (Davis, Science, 1901.) 



MOUNTAIN BORDER AND INTERNAL STRUCTURE 

A condition of first importance in determining the origin and physio- 
graphic aspects of the Basin Ranges is the manner in which the border 

1 In an attempt to formulate the principles that should guide the interpretation of such 
forms, Davis has made an elaborate study of the theoretic problem of the explanation of fault- 
block mountains. The block diagrams from that paper (W. M. Davis, The Mountain Ranges 
of the Great Basin, Bull. Mus. Comp. Zobl., vol. 42, Geol. Surv., vol. 6, 1906), reproduced 
here, very clearly present the main problems associated with the three elements necessarily 
involved in the problem of block faulting — the pre-f ault topography, the topographic effect of 
the faulting, and the degree of dissection of the faulted blocks. The paper includes a compari- 
son of the base line of residual mountains with that of fault-block mountains; a description of 
the canyons and ravines of block mountains; and the order of development and means of de- 
termination of spurs and terminal facets. 



224 FOREST PHYSIOGRAPHY 

of each range cuts across the internal or primary structure so that the 
structure is very commonly oblique to the mountain front, Fig. 58. 
It is a safe inference that there can be in such a case no direct relation 
between the trend of the range and its primary structure, otherwise 
there should be a certain harmony between them, such as exists for ex- 
ample between the strike of resistant strata in the Appalachian Moun- 
tains and the trend of the ^Appalachian ridges. 

CONTINUITY OF RANGE CREST 

One of the most important indications of the origin of the Basin 
Ranges through block faulting of later date than the internal structure 
of the ranges is the fact that the body of each range is usually con- 
tinuous although incised by sharply cut valleys. If the mountain 
ranges were residuals of a period of long-continued and undisturbed 
erosion such as must be postulated if the broad intermont valleys are 
explained by erosion, each range should be dissected into a number of 
short mountain ranges and isolated peaks. Stream action profound 
enough to excavate the broad intermont valleys would produce in the 
same time equally profound differential erosion in the body of the 
ranges. On the other hand, had the region been reduced at one time to 
a lowland of faint relief and the relief still further reduced by lava out- 
pourings, the formation of great fault blocks would result in broad and 
flat intermont valleys as conspicuous as the ranges between which they 
lie, and the ranges themselves, if not too maturely dissected, would 
possess a marked rectilinear quality.^ 

THE OREGON RANGES EXHIBIT CRITICAL FEATURES 

The indifference of mountain border to internal structure, and the 
continuity of the individual ranges, are both seen to best advantage in 
southern Oregon. In most parts of the Great Basin the typical basin- 
range structure produced by the faulting and tilting of long narrow 
crust blocks is largely obscured by erosion or by the topographic effects 
of complex internal folds and faults. In south-central Oregon, how- 
ever, the crust blocks have been deformed so recently that erosion has 
but slightly modified them, and no internal deformation in the body of 
the blocks preceded the faulting.^ 

In the bedded lavas of Lake County, Oregon, topographic features ^ 
occur which seem closely related to a great upward fold or anticline 

1 W. M. Davis, Current Notes in Physiography, Science, n. s., vol. 14, 1901. 

2 Idem. 

' G. A. Waring, Geology and Water Resources of a Portion of South-Central Oregon, Water- 
Supply Paper U. S. Geol. Surv. No. 220, 1908, p. 25. 



GREAT BASIN 225 

which has been extensively faulted in places. Chewancan River has 
cut its channel along the axis of the fold for a number of miles. In 
Summer Lake Valley the anticline is broken down, the western side re- 
maining in place to form Winter River Valley, while the eastern is buried 
beneath lake deposits. Goose Lake Valley lies on the dropped key- 
stone of the anticlinal arch, its eastern side being marked by a steep 
slope, its western side by a longer monoclinal slope.^ 

An immediate result of the earth movements by which the ridges were formed was the for- 
mation of a large number of enclosed basins whose floors are now occupied, to some extent, by 
lakes. There are ail gradations between basins so small and poorly supplied with water that 
none whatever accumulates on the basin floor, and basins in which the rainfall is sufficient to 
maintain either temporary or permanent alkaline or sahne lakes; or, as in the case of Goose 
Lake basin, a water supply sufficient to cause the basin occasionally to drain into the sea. 
Distinct shpre terraces indicating the level of ancient Quaternary lakes that once existed here 
are to be found on the slopes of many of the basins. 

EVIDENCES OF PROGRESSIVE AND RECENT FAULTING 

BROKEN WASTE SLOPES 

Not only have the Basin Ranges been blocked out by great faults, but 
faulting has continued down to the present. It is expressed among 
other ways in broken fans at the foot of the scarps which form the 
range fronts. Such broken fans have been noted repeatedly in glacial 
and postglacial deltas and fans along the base of the Wasatch Mountains, 
as in the delta of Rock Canyon Creek near Provost.^ Low escarpments 
in lacustral beds and alluvial slopes in places form irregular lines along 
the bases of the mountains, and at times cross the valleys. They present 
a small cliff or steep ascent between two nearly horizontal plains.^ The 
crests of the scarps are always irregular and sometimes form zigzag 
lines that may be followed for miles; they are fault scarps of very late 
origin. In many cases it is believed that they could not have existed in 
their present condition more than a few years. Sometimes they are 
more than a hundred miles long and vary from a few feet to more 
than a hundred feet in height.* That they are recent fault scarps is 
shown by the fact that they commonly occur in Quaternary lake de- 
posits and recent alluvial slopes but little modified by erosion; and 
in many instances they are without vegetation. Similar scarps have 
been observed at the eastern base of the Sierra Nevada and at the foot 

1 G. A. Waring, Geology and Water Resources of a Portion of South-Central Oregon, 
Water-Supply Paper U. S. Geol. Surv. No. 220, igo8, p. 26. 

2 W. M. Davis, The Mountain Ranges of the Great Basin, Bull. Mus. Com. Zoo!., vol. 
42, p. 160. 

' I. C. Russell, Geological History of Lake Lahonton, a Quaternary Lake of Northwestern 
Nevada, Mon. U. S. Geol. Surv., vol. 11, p. 274. 
* Idem, p. 375. 



226 



FOREST PHYSIOGRAPHY 



of the slopes of many of the Basin Ranges. In the Lahonton area recent 
fault scarps are a common feature in the topography of the valleys. 
Fig. 54. Scarps of a similar nature were first observed in the Great 




Fig. 59. — Post-Quaternary fault on the south shore of Humboldt Lake. (Russell, U. S. Geol. Surv.) 

Basin by Gilbert and were recognized as the result of recent crustal 
movements.^ 

The recent faults of the Basin Ranges occur most commonly on the steeper sides of the 
mountains and invariably the throw is toward the valley. Occasionally they cross stream 
channels and cause rapids, as in the case of the American Fork, Utah, where it crosses the 
Wasatch fault. The distribution of recent faults is in marked sympathy with the ancient 
lines of displacement as determined by evidences of a topographic character such as have 
just been outlined. But it should be remembered that the recent faults are but a small frac- 
tion of the entire displacement. 



STREAM PROFILES AND RECENT FAULTING 



Among the significant elements of topographic form indicative of 
recent faulting are the abnormal profiles of many stream channels cross- 
ing the fronts of the fault blocks. Prolonged erosion of a stable block 

J Second Ann. Rept. U. S. Geol. Surv., 1880-1881, p. 192. 



GREAT BASIN 



227 



mountain would result in the development of stream gradients of the 
normal type whose descent from the headwaters of the region would be 
progressively more and more gentle. In the Basin Ranges, however, 
it has been frequently noted that the stream gradients are distinctly 
abnormal, and that they are notably peculiar in that a V section per- 
sists down to the mountain base where the steep-sided ravines suddenly 
open upon gravel fans that form parts of wide piedmont alluvial 
plains. Typical examples occur in the Pueblo range and in the Weber 
and Ogden canyons of the Spanish Wasatch. It is noteworthy that the 
steep-walled canyons that appear near the base of the range are in con- 
trast with the upper portions of the valleys where flatter gradients occur. 
It appears that the progressive elevation of the fault-block mountains 
causes progressive down-cutting on the part of the draining streams. 
This lack of stability in the mountain mass and constant rejuvenation 
of the streams by repeated uplift prevent the streams from widening 
their valleys to the normal form. 

TERMINAL FACETS OF THE MOUNTAIN SPURS 

Another feature indicative of progressive faulting is the occurrence 
of terminal facets of peculiar and significant character and of very per- 




Fig. 60. 



- Ravines, spurs, and terminal facets of the Spanish Wasatch, looking east. Note the even 
base line developed on rocks of varying resistance. (Davis, Bull. Mus. Comp. Zool.) 



feet development. In the case of the Spanish Wasatch the facets slope 
at an angle of 38° or 40°, are of remarkably regular occurrence and form, 
and are set off from each other by deep ravines that diversify the 
mountain front. The base line of this range is almost rectilinear, a 
feature in itself of the greatest importance in the interpretation of the 
morphology of a mountain mass whose structure possesses sufficient 
diversity to occasion under ordinary conditions topographic irregu- 
larities of considerable degree. 



2 28 FOREST PHYSIOGRAPHY 

SPRINGS AND FAULT LINES 

Throughout the entire Great Basin there is a rather intimate asso- 
ciation between thermal springs and lines of recent faulting; and the 
hottest springs almost invariably occur on the lines of displacement 
that have suffered most recent movement.^ This relation of thermal 
springs to recent faults along the bases of the frontal scarps is almost 
constant and is in entire sympathy with the explanation of continued 
block faulting in the Great Basin region.^ 

FEATURES OF THE DEATH VALLEY REGION 

If we now turn to other ranges in the Great Basin than those we 
have thus far noted we shall find a striking persistence of the structural 
and physiographic features already examined. In the Death Valley 
region the fault-block type of structure and topography has been clearly 
identified. The strata of this region suffered deformation (Eocene) 
in which faulting and tilting took place and parallel mountains and 
valleys formed that trend northwest in the general direction of the 
Sierra Nevada. Deformation of any type tends to produce enclosed 
basins and in an arid climate this tendency is usually realized in a pro- 
nounced way. In the Death Valley region faulting and tilting produced 
enclosed basins in which lakes were formed and lake sediments de- 
posited to a thickness of several thousand feet. These lake sediments 
include great deposits of salt, gypsum, soda, and borax. Later still 
(Miocene) another period of deformation set in. It was characterized 
by faulting and tilting as in the earlier period of deformation but along 
lines more nearly north than before and parallel with the basin ranges. 
Immense mountain ranges were the result, such as the Funeral and 
Panamint ranges, with the Panamint, Detah, and Amaragosa valleys 
between them. In the enclosed basins that were thus formed lakes 
existed for a time, and on their floors and about their borders were 
deposited sediments similar to those of the earlier lake period.^ 

1 I. C. Russell, Mon. U. S. Geol. Surv., vol. ii, 1885, p. 276. 

2 The relation of hot springs to recent faulting is brought out clearly in a map of the 
United States published in 1875: Report upon Geographical and Geological Exploration and 
Surveys West of looth Meridian, Wheeler Surveys, vol. 3, Geology, 1875, pp. 148-150. Sixty- 
seven springs occur in the western region and but 15 in the eastern. Forty-seven of the first 
group have a temperature as high as 100° F.; only 2 in the latter group reach this temperature. 
The areas are in the ratio of 13 to 3. If the country were better known the ratio would show 
an even greater preponderance of springs in the western region. 

3 M. R. Campbell, Basin Range Structure in the Death Valley Region of Southeastern 
California (Abstract), Bull. Am. Geol. Soc, vol. 14, 1903, pp. 551-552. 



GREAT BASIN 229 

Soils of the Great Basin 

The soils of the Great Basin are derived from a great variety of rocks,, 
and consist of colluvial wash of the mountain slopes, thick lacustrine 
and shore deposits associated with ancient Lake Bonneville, and recent 
stream-valley sediments and river-delta deposits. When not situated 
above or outside the limits of irrigation, or rendered unfit for cultiva- 
tion by accumulations of alkali or seepage waters, they are of great 
agricultural importance. 

The soils of alluvial cone deposits are usually gravelly and very dry, 
and therefore treeless, except in the immediate vicinity of stream courses. 
The more elevated areas are frequently rough and hilly and marked by 
the presence of rock outcrop and bowlders. They are frequently cut 
by washes or intermittent stream channels, and are well drained, except 
in the lower-lying areas occupying depressions. 

The soils of lacustrine sediments and material derived from stream 
deltas occur upon low, level plains, marking the site of recent lake 
bottoms. They are generally barren, deficient in drainage, and heavily 
impregnated with alkali salts. They are derived from eruptive, sedi- 
mentary, and altered rocks of various ages and are without gravel. 
They cover extensive areas, are usually dark in color, and in general 
have little or no agricultural importance. 

The soils formed of colluvial mountain wash or of residual material 
mingled with alluvial deposits of intermittent or torrential streams are 
often gravelly, sometimes marked by rock outcrop, and frequently cut 
by washes and intermittent stream channels, and generally treeless. 
The soils are derived primarily from red sandstone, modified in places 
by an admixture of material derived from shales, slates, eruptive rocks 
etc., and are typically of vermilion or bright-red color. They occur 
generally as extensive areas. The lower-lying and heavier soils are 
often poorly drained and alkaline. 

Along valley troughs and in the vicinity of river flood plains, stream 
sediments of recent origin or in process of formation form an impor- 
tant group of soils. They occupy low or slightly elevated valley plains, 
have a smooth, nearly level surface, and are frequently marked by the 
presence of stream channels or sloughs. They are derived mainly from 
eruptive, early sedimentary, and altered sedimentary rocks, are gener- 
ally dark in color, and are underlain by light-colored sands or sandy 
loams or by heavy red subsoils. 



230 



FOREST PHYSIOGRAPHY 
Forests and Timber Lines 



The high barrier of the Sierra Nevada on the windward side of the 
Great Basin so reduces the rainfall on the lower Basin Ranges as to 
make the forest growth thin and scattered or wholly absent. No large 
and dense forests occur in the province, Fig. 6i. The existence of a 




Forest 
reservations 

Fig. 6i. — Location of vacant public land. Note the disproportionately large amount of vacant public 
land in the Great Basin. (Newell, Irrigation in the U. S.) 

forest is conditioned by the amount of rain that falls on each range. 
As a whole the province is not one whose forest growth is of great 
importance to lumbermen; but the very scarcity of forests in so arid 
a region makes doubly important the study of the physical conditions 
surrounding the isolated forests that do exist. 

In the arid Great Basin a lower timber line and an upper timber line 



GREAT BASIN 



231 



are clearly defined on most of the mountain ranges. The position of 
the upper or cold timber line is determined mainly by the annual tem- 
perature of 32° F., but has some variation depending upon differences 
in snowfall, soil conditions, severity of winter storms, and exposure to 
the sun. The vegetation above the cold timber line is commonly alpine 







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Fig. 62. — Approximate location and extent of open range in the West. (Newell, Irrigation in the U. S.) 

flowers and grasses of various sorts up to the lower limit of snow.^ 
The lower limit of tree growth may be called the dry timber line, 
although to drought is added the influence of cultivation, soil conditions, 
alkali, hot winds, exposure to the sun, etc. Unlike the cold timber line, 

' This line is at sea level in Alaska and northern Canada, where it defines the polar limit 
of the subarctic forest and may be called the " continental timber line." North of it is a zone 
of tundra and barren grounds corresponding to the zone of alpine flowers above the cold 
timber line on the mountain slopes and summits of temperate latitudes. 



232 



FOREST PHYSIOGRAPHY 



the dry timber line may be independent of latitude and altitude, its 
position depending almost entirely upon the amount of rainfall. Below 
the dry timber line of the Great Basin are, in some cases, treeless, 
grassy to arid plains and valleys, while in other cases the dry tree line 
merges into the zone of juniper. In central Idaho the cold timber 
line is at 10,000 feet, the dry at 7000 feet. Its position in the 
Prairie Plains province in eastern Kansas and Nebraska is dependent 
upon the gradual increase of rainfall eastwardly from the Rockies and 
High Plains. The dry timber line disappears in humid regions, as in 




Fig. 63. • 



■Typical view oi desert vegetation, southern Great Basin, near Goldfield, Niev. 
(Ransome, U. S. Geol. Surv.) 



the Adirondacks and the White Mountains. The meeting of the dry and 
the cold timber lines on those ranges in the Great Basin that are both 
cold above and excessively dry below, as the White Mountains of 
western Nevada, Plate IV, results in the complete absence of forest 
growth.^ 

While the upper timber line is determined usually by temperature, other 
factors may have a determining local influence and in nearly all cases 
have an important influence. Among these factors are the slopes of the 
surface, the degree of exposure to the sun, the depth of the snow, the 

' I. C. Russell, Timber Lines, (Abstract) Bull. Geol. Soc. Am., vol. 14, igo3, pp. 556-557. 



GREAT BASIN 233 

severity of the winter storms, etc., though the dominant cause is the 
low temperature.^ 

The most abundant and most generally distributed trees from the 
western foothills of the Wasatch Mountains in eastern Utah to south- 
eastern California, northern Arizona, western Colorado, and southern 
Wyoming are the juniper and the nut pine {Pinus monophylla) . In 
central Nevada the juniper often descends into the valleys and forms 
open stunted forests at elevations of about 5000 feet. It is more abun- 
dant and of larger size on arid slopes at elevations of 8000 feet above 
the sea, where it occurs in dense and nearly pure forests.- The nut 
pine, or pinon, occurs on dry gravelly slopes and mesas throughout the 
same territory, often forming extensive open forests at elevations between 
5000 and 7000 feet.^ 

From the commercial standpoint the most important trees in the 
Great Basin are the yellow pine and Douglas spruce, but their growth 
is limited to the higher ranges of the provinces where they form open 
woodland, never a true forest. A typical growth is found on the Snake 
Range which lies just west of the Nevada-Utah line, trends north and 
south, and is about 135 miles long. It contains the highest peak be- 
tween the Wasatch and Sierra Nevada, Jeff Davis or Wheeler Peak, 
more than 12,000 feet high, besides being one of the most rugged ranges 
in the Great Basin."* The intermediate slopes. Fig. 64, are covered with 
a tree growth. Alpine fir, white fir, Douglas fir, and Engelmann 
spruce are the principal species, yellow pine being relatively scarce and 
limited to the lower elevations. The higher portions of the range are 
almost devoid of vegetation owing to the low temperature. The cold 
timber line lies at 10,500 or 11,000 feet. It should not be considered a 
definite line, however, since the forest disappears on the dry spurs at 
much lower elevations than in the wet canyons. The dotted line near 
the summit in Fig. 64 represents the upper limit of growth in the can- 
yons. The foothill belt below the dry timber line is covered with sage- 
brush and bunch-grass. The valleys have a better growth of grasses, 
while the springs and streams are lined with shrubs and aspen and a few 
cottonwoods. 

By far the greater number of the Basin Ranges are desert or support 

1 For a discussion of this matter see I. C. Russell, Timber Lines, Nat. Geog. Mag., vol. 15, 
1904, pp. 47-49; for a criticism see C. H. Merriam, Nat. Geog. Mag., vol. 14, 1903. 

A "wet timber line" may also be identified about the borders of lakes, swamps, etc. 

2 C. S. Sargent, Manual of Trees of North America, 1905, p. 89. 

3 Idem, p. 12. 

^ J. E. Spurr, Descriptive Geology of Nevada South of the 40th Parallel, Bull. U. S. 
Geol. Surv. No. 208, 2d ed., 1905, p. 25. 



234 



FOREST PHYSIOGRAPHY 



only a scanty growth of sage-brush and juniper and a few stunted pines 
near the summit. They have only a very scanty supply of water and 
a few widely separated springs.^ The Cedar Mountains west of Salt 
Lake Valley afford typical conditions. 

The Montezuma Range in western Nevada also illustrates this type 
of range. Only a few stunted pines and junipers are found and these 
grow only on the upper slopes and in the more sheltered canyons. The 






^^ 



Fig. 64. — East side of Snake Range, Nevada. Jeff Davis or Wheeler Peak from Robinson's Ranch. 
Yellow pine comes in on the lower edge of the timbered belt and Alpine fir, white fir, and Engelmann 
spruce are the principal species at higher levels. (U. S. Geol. Surv.) 

range lies not far from the great Sierra Nevada on the west and in spite 
of its bold appearance provokes but little rainfall from the winds that 
pass the higher topographic barrier on the west. The range is one of 
the driest in Nevada.^ Excellent grass is abundant, however, and has 
high value for grazing, but in order to supply stock precautions must 
be taken to prevent spring waters from running to waste. 

Many of the Basin Ranges with intermediate elevations have impor- 
tant forest tracts even though a continuous forest cover is wanting. 

I S. F. Emmons, Desert Region, Descriptive Geology, vol. i, 1877, p. 462 (King Surveys). 
' Arnold Hague, Descriptive Geology, vol. 2, 1877, p. 752 (Hayden Surveys). 



GREAT BASIN 235 

The Schell Creek Range, for example, has closely restricted patches of 
yellow pine and fir in the moister canyons and small upper basins. 
While these are not important in a large way, they at least supply a 
most important need on the part of the ranchmen, farmers, and miners 
engaged in developing resources near by. 

The most prominent range between the Sierra Nevada and the Wasatch 
is the East Humboldt Range in central Nevada. It is a bold, single 
range about 80 miles long with many summits reaching over 10,000 
feet. Because of its relatively high altitude and its greatly dissected 
condition it has a more alpine aspect than the other Basin Ranges and, 
as compared with the lower ranges about it, receives more rainfall and 
snowfall. In response to the heavier precipitation it supports an open 
tree growth. Its higher canyons and upper slopes are covered with 
scattered forests including several varieties of pines and firs, among 
which the limber pine {Pinus flexilis) is the prevailing species. The 
trees do not, however, supply much valuable timber since they are 
knotty and rarely over 50 feet high.^ 

1 Arnold Hague, East Humboldt Range, Descriptive Geology, vol. 2, 1877, p. 528 (King 
Surveys). 



CHAPTER XV 

LOWER COLORADO BASIN 

On account of the scarcity of arboreal vegetation in the lower Colo- 
rado Basin and the close genetic relationship of its forms with those of 
the Great Basin already somewhat fully discussed we shall devote but a 
few paragraphs to its physiography. The province includes (i) an 
eastern section of low, residual mountains, piedmont slopes, and inter- 
montane basins forming the southwestern portion of Arizona, and (2) a 
western section of interior basins west of the Colorado and north of the 
mountains of dry southern California. 

The mountains of the eastern section are regarded as of the basin- 
range type — fault-block mountains originally like those of south- 
eastern Oregon. They are, however, much older than the latter and are 
so thoroughly dissected that their original asymmetry has been lost. 
The broad structural valleys between the ranges have been in part 
floored by piedmont and basin deposits in part extended by rock pla- 
nation, a result attributed to sheet-fiood erosion.^ The basin floors in the 
Sonora district of Mexico and Arizona, where the half-buried mountains 
rise above broad plains, appear at first to be wholly alluvial. More 
intimate examination shows that only half of their surface is covered with 
alluvium; the other half is in reality planed rock. Two-fifths of the 
entire area including both plains and mountains is smoothly-beveled rock 
floor, the rock being granite, schist, and other types, planed off in a belt 
from 3 to 5 miles wide which merges with the alluvial portion of the basin 
on the one hand and from which the mountains rise sharply without 
any intervening foothills on the other. The graded character of the 
floor is no doubt to be ascribed to water action, as was insisted by 
McGee; but the fact that the surface of the rock floor on the basin 
margins is kept relatively free from alluvium should probably be as- 
cribed in large part to wind action which is universal and almost 
constant. ' 

A peculiar feature of many of the basin floors of the arid region is 
the gravelly appearance of the surface. Gravels and small bowlders 

^ W J McGee, Sheet-flood Erosion, Bull. Geol. Soc. Am., vol. 8, 1897, pp. 87-112. 

236 



LOWER COLORADO BASIN 237 

are found scattered over the higher slopes of nearly all the intermont 
valley plains. The general appearance is that of a vast gravel bed. It 
is not uncommon to find an area several acres in extent covered with 
small angular stones as closely and evenly set as mosaics. The pebbles 
constituting the gravel are, however, but a thin surface veneer. The 
wind constantly blows away the fine material and is unable to remove 
the coarse, which accumulates as a protective cover. The pebbles are 
sometimes only one deep, and below them there is often a fine porous 
loam which may be of great fertility.^ 

It is estimated that about 85 % of the entire surface of the eastern 
section of this province (east of the Colorado River) is plain and about 
15% is mountains. Such an excess of low over high country in an arid 
region means that the mountain-born streams will quickly wither on the 
plains and that trunk streams will be either rare or wanting altogether. 
Where the mountains are low, the streams are insignificant in size and 
disappear almost at the mountain bases. Except the Gila and the 
Colorado, which have their sources in high and well-watered country, the 
Lower Colorado Basin has no through-flowing streams; the majority of 
its streams are of the type of "lost rivers" which disappear by absorp- 
tion and evaporation before reaching the sea. 

The western section of the pro\dnce beyond the Colorado is excep- 
tionally arid and hot and includes the Mohave desert. The rivers ter- 
minate on the piedmont slopes of the desert ranges or feed permanent salt 
lakes or the temporary lakes of salinas and playas (see Fig. 27). 

Types op Lowlands 

The portion of the Lower Colorado Basin that lies in Arizona con- 
tains three distinct kinds of lowlands: (i) valleys and canyon floors 
now containing running water such as the Colorado and Williams 
valleys and Santa Maria Canyon; (2) old, deeply filled, alluvial vaUeys 
such as the Sacramento and the Big Sandy; and (3) plains of erosion 
such as those that in many places border many of the desert ranges and 
are due to sheet-flood erosion. Among the intermontane plains are 
Cactus, Posas, and Ranegras plains, etc. They are in part old, deeply 
filled valleys that have a general altitude of about 2000 feet toward the 
plateau region on the east and gradually descend westward to about 
400 feet at the Colorado River. All of them have been somewhat modi- 

1 C. R. Keyes, Rock Floor of Intermont Plains of the Arid Regions, Bull. Geol. Soc. Am., 
vol. 19, 1908, pp. 63-92. See also C. F. Tolman, Erosion and Deposition in the Arizona Bol- 
son Region, Jour. Geol., vol. 17, 1909, p. 14. 



238 FOREST PHYSIOGRAPHY 

fied by crustal disturbances and basaltic extrusions from many local 
centers of igneous activity.^ 

One of the largest of these valleys is the Detrital-Sacramento Valley 
which extends north and south parallel to the Colorado River for more 
than 100 miles. It is interrupted here and there by lava masses, but its 
material consists chiefly of gravel filling of great depth. It is in a region 
of profound faulting and warping, and may have originated as a suc- 
cession of structurally depressed areas. Whatever its origin it has been 
greatly modified by a stream of considerable size which has almost 
filled the entire bottom of the valley with an enormous amount of detri- 
tal material. This work may have been accomplished by the Colorado 
or by some stream now extinct, a fact which has not yet been safely 
determined. 

SPECIAL DRAINAGE FEATURES 

The lower valley of the Colorado River, that portion which crosses 
the Lower Colorado Basin, is remarkable for extreme irregularity of 
topography within short distances. It consists of a series of narrow, 
steep-walled gorges, and broad alluvial basins through which the river 
winds in an exceedingly irregular course. It is concluded- that at one 
time the Colorado River ran through the present Detrital-Sacramento 
Valley, that it filled this valley and adjacent depressions with a pro- 
digious quantity of alluvial material, and when, on account of changed 
climatic or geologic conditions or both, the river began again to degrade its 
channel it occupied its old valley throughout the greater part of its course; 
but at certain places, as in Pyramid Canyon, Eagle Rocks (Fig. 65), and 
other localities farther south, its course at the moment of change from 
aggradation to degradation was directed across alluvium-buried moun- 
tain spurs and knobs. With the progress of down-cutting these spurs 
and knobs were uncovered and the course of the river across or through 
them is now marked by narrowness, bank declivity, hard rock, and steep- 
ened gradient, instead of the flat gradients of the alluvial bed and the 
wide flat-floored valleys that elsewhere characterize its course. 

The Colorado River is to-day carrying immense quantities of silt 
which it is spreading over its rapidly aggrading flood plain. The river 
carries more suspended matter per unit volume than any other stream 
in North America — 2000 parts of sediment per 100,000 parts of water, or 
enough in one year to cover 164 square miles i foot deep with mud. 

1 W. T. Lee, Geologic Reconnaissance of a Part of Western Arizona, Bull. U. S. Geol. Surv. 
No. 352, 1908. 

2 Idem. 



LOWER COLORADO BASIN 



239 




Fig. 6s. — Map of part of Colorado Valley, showing old gravel-filled channel on right and rock channel 
on left. (Lee, U. S. Geol. Surv.) 



The rapidity of filling of the Colorado River on its flood plain is indicated in many places 
where lateral cutting exposes the roots of trees and shrubs now buried to a greater or less 
degree. In many places living arrow weeds may be seen standing in five feet or more of silt. 
The material is well stratified and exceedingly fine. When deposited in thick beds it dries 
and cracks in great columns two or three feet in diameter, the cracks themselves being several 
inches wide and two feet or more deep. 



240 FOREST PHYSIOGRAPHY 

The river frequently changes its course over the wide bottom lands 
which it drains, sometimes by normal lateral cutting and sometimes 
by more intense erosive action during a period of high water. These 
changes result in the formation of new channels, the abandonment of 
old ones, the formation of cut-off meanders, sloughs, lagoons, ox-bow 
lakes, and dry channel courses. 

But little of the land along the Colorado is irrigated because the 
river and its tributaries are in general so far below the bordering lands 
as to render diversion extremely difficult or impracticable. At Yuma 
two pumping plants lift water from the river for irrigation and several 
other lifting plants are located below this point. The Imperial Canal 
diverts water from the river at a point about lo miles below Yuma.^ 

The Colorado is subject to annual overflow from April to June and 
may spread out over the Salton region of the Colorado desert forming 
lakes. Mearns noted (1892-1894) that these lakes eventually dried 
up, but for a long time after the water had disappeared the region 
was green and vegetation throve in the rich surface deposits. Cattle 
Avere driven in and the owners endeavored to make a breach in the 
Colorado River bank at each annual overflow, so that the region became 
flooded through the channels of New and Salton rivers, causing a fresh 
crop of forage plants to spring into life.^ 

Salton Sink Region 

That portion of the Lower Colorado Basin known as Salton Sink is 
of special interest because it contains one of the two tracts of land in 
the United States below sea level. 

The Salton Sink region contains two fertile valleys, the Coachella Val- 
ley in Riverside County northwest of Salton Sink, and the Imperial 
Valley in Imperial County southeast of Salton Sink. Lying partly in 
each of these two counties is Salton Sea, the bottom of which is 273.5 
feet below mean sea level. ^ 

In recent geologic time Salton Sea was a part of the Gulf of Cali- 
fornia which then extended about 200 miles farther northwest than at 
present. At that time the mouth of the Colorado was near Yuma, 
60 miles from its present location, and was gradually building a delta 

1 Freeman and Bolster, Surface Water Supply of the United States, igoy-oS, Colorado 
River Basin, Water-Supply Paper U. S. Geol. Surv. No. 249, pt. 9, 1910, p. 34. 

2 E. A. Mearns, Mammals of the Mexican Boundary of the United States: A descriptive 
catalogue of the species of mammals occurring in that region, with a general summary of the 
natural history and a list of trees, Bull. U. S. Nat. Mus. No. 56, pt. i, 1907, p. 28. 

3 Freeman and Bolster, Surface Water Supply of the United States, 1907-08, pt. 9, Colorado 
River Basin, Water-Supply Paper U. S. Geol. Surv. No. 249, 1910, pp. 46-51. 



LOWER COLORADO BASIN 241 

that extended southwest toward the Cocopa Mountains. Deposition 
continued until the upbuilding of this delta had completely separated 
the head from the rest of the gulf and converted its floor into an in- 
land sea. Delta growth continued until the inland lake became not 
only entirely independent of the Gulf but also actually raised to a 
higher level than the sea. Consequently one may see to-day faint 
terraces in favorable places on the margin of the depression, and on 
rocky points is a thin deposit of calcium carbonate and slightly cut sea 
cliffs about 40 feet above sea level. Even some of the alluvial cones 
formed on the shore line had beaches which, although easily eroded, 
are even now well preserved, an indication of their recent formation; 
and over the floor of the desert and along the sandy beaches are 
thousands of shells of fresh- or brackish-water mollusks.^ The water 
of the lake was not perfectly fresh, for it is estimated that the evapora- 
tion from its surface nearly equaled the average annual inflow from the 
Colorado, and even if the flow of the river exceeded this evaporation 
it could not have done so by a large amount; in either case the waters 
of the lake would be markedly alkaline. This is also shown by the 
fact that wherever the lake waters broke in spray and evaporated 
more rapidly than usual, carbonate of lime was deposited. It is known 
from the extent of the delta that the river broke out of its channel 
many times while building it and alternately discharged into the Gulf 
of California and the Salton Sea. During those periods in which the 
river discharged into the Gulf of California, Salton Sea must have con- 
tracted and become more and more alkaline. The last natural dis- 
charge of the Colorado into Salton Sink was of very recent occurrence. 
It is probable that the lake which it supplied existed but little more 
than a thousand years ago. In recent years we have had well-known 
instances of changes. 

During the summer of 1891 the Colorado overflowed into Salton Sink at the time of high 
water to such an extent as to endanger the Southern Pacific Railway line; and in the summer 
of igo5, after a number of winter and spring floods in the Gila River and a heavy summer flow 
in the Colorado, the floods were repeated on a much larger scale. The gravity of the situation 
was increased by the existence of diverting canals which conveyed water to the Imperial Valley 
from the Colorado. The canals were not provided with protective headworks, and had a 
gradient much greater than that of the river, so that after the flood of 1905 and in July the main 
canal was carrying 87% of the total flow of the river, and the water was deepening and widen- 
ing the Alamo River, along which the canal extended, to a great gorge. Strong efforts by the 
Southern Pacific Railway Company resulted in the control of the Colorado in the early fall of 
1906, but it broke out again on December 7, and was only closed finally in February, 1907. On 
December 31, 1908, the surface of the Salton Sea was still far above its normal level, being only 

1 R. E. C. Stearns, Remarks on Fossil Shells from the Colorado Desert, Am. Nat., vol. 13, 
1879. PP- 141-154- 



242 



FOREST PHYSIOGRAPHY 





PEC^ AMOTION SERVICE USGS 
FIEUltF MAP OF THE 

LOWER COLORADO RIVER, 
SHOWING irrigable: LANDS 

'IN THE 

UNITED STATES a MEXICO. 



/ //I I \ \ \ 




6 u L r o r 

C A L I F O R N i 



Fig. 66. — Map of the Salton Sink region, California. (U. S. Geol. Surv.) 



2o6 feet below mean sea level. It then had a maximum depth of 67.5 feet and an areal extent 
of about 443 square miles. Its temporary enlargement necessitated shifting the Southern 
Pacific tracks over a stretch about forty miles long, a stretch that was originally constructed 
on the 200-foot contour below sea level. Another line has since been survej'ed and graded on 
the 150-foot contour below sea level for possible use in the future. The Sea has also com- 
pletely submerged the plant of the New Liverpool Salt Company and a few ranches near Mecca.' 



1 Freeman and Bolster, Water-Supply Paper U. S. Geol. Surv. No. 249, 1910, pp. 50-51. 



LOWER COLORADO BASIN 243 

So completely cut off from the rest of the Gulf of California was the 
Salton Sink region before 1905 that the waters of the beheaded section 
of the ancient gulf were evaporated to the point where only a fragment 
of the original water body remained. Its waters were until recently 
exceedingly salty and the shores of the lake or sink were fringed with 
wide, white belts of salt-incrusted land. Only a few trifling streams 
descend from the higher portions of the San Bernardino and San Jacinto 
mountains to feed the dwindling remnant of what was once a great water 
body. In Fig. 66 is represented the maximum size of the ancient water 
body as recorded in a well-preserved strand line that contours evenly 
about the margin of the basin. 

Climate, Soil, and Vegetation 

The following data on the relief, climate, and vegetation of the south- 
ern border of the Lower Colorado Basin are compiled mainly from the 
excellent work of Mearns.^ They are typical of the relations of topogra- 
phy, rainfall, and vegetation over a much wider area and deserve close 
examination by the student of forestry. 

The mountains of the southeastern portion of the Lower Colorado 
Basin form continuous rajiges rising very sharply from the plains. 
They are seldom well forested because of the steepness of their slopes, 
from which the soil is blown or washed away almost as fast as formed, 
leaving the bare rocks without vegetation except in crevices, benches, 
and hollows. 

The soils of the region are mainly of colluvial, alluvial, and lacustrine 
origin, modified by the addition of recent stream sediments; they are 
without important amounts of humus owing to the aridity. They 
occupy mountain foot slopes, alluvial fans, debris aprons, or sloping 
plains of filled valleys, sloping or nearly level plains, and bottoms of 
stream valleys or sinks and drainage basins. Since the climate of the 
arid Southwest is characterized by semi-tropical desert conditions, the 
soils have little or no value save as they can be irrigated or as they 
occur in limited amounts in rock crevices, etc., and as a thin veneer 
on higher slopes where the rainfall makes a thin forest growth 
possible." 

There is a very thin population along the entire boundary, the only towns near it being 
Bisbee, Santa Cruz, Nogales, Yuma, and San Diego. Except for these towns and a score of 
small settlements in the principal valleys the zone of 24,000 square miles along the boundary, 
20 miles on either side, contains less than 100 permanent inhabitants. 

1 E. A. Mearns, Mammals of the Mexican Boundary of the United States: A descriptive 
catalogue of the species of mammals occurring in that region, with a general summary of the. 
natural history and a list of trees. Bull. U. S. Nat. Mus. No. 56, pt. i, 1907. 

' Soil Survey Field Book, U. S. Bureau of Soils, igo6. 



244 FOREST PHYSIOGRAPHY 

The average precipitation along the entire boundary is about 8 inches 
and on the Yuma and Colorado deserts it is but 2 or 3 inches. For 
700 miles between the Rio Grande and the Pacific, the boundary line 
is crossed by only five permanent running streams although it crosses 
the mountain ranges nearly at right angles, a direction most favorable 
for encountering existing streams. There are two periods of rainfall, 
one in midwinter and one in midsummer, the midsummer rainy period 
being known as the rainy season. The summer rains generally begin 
about the first of July and last until the middle of September. Soon 
after the first rain falls the vegetation assumes a spring-like aspect, 
leaves burst forth, hills and valleys are covered with grass, and a be- 
wildering profusion of wild flowers covers the surface. The plants 
grow with great rapidity, their seeds mature before the rains cease, and 
in a month or so after the rains have stopped they have the somber 
colors typical of fall and winter. 

On the whole the Mexican boundary district of the Lower Colorado 
Basin is treeless; the forests are confined almost entirely to the moun- 
tain ranges and the stream courses, but those in the latter situation are 
few in number and of insignificant size. On some of the desert spaces 
arboreal cacti and yuccas form open groves. The streams are lined with 
Fremont cottonwood, black willow, box elder, walnut, sycamore, oak, 
mulberry, ash, etc. Among these the cottonwood and willow are found 
on every permanent stream, and are usually flanked by a broader zone of 
mesquite. The desert willow, hackberry, and indigo tree are found in 
arroyos in which there is a slight amount of moisture. 

There are a few large alkali flats perfectly bare of vegetation and a 
number of spots in the desert are without plants, but over the great 
stretch of desert country between the Gila Mountains and the Colorado 
River there are found almost everywhere four species of plants — the 
creosote bush, the sage, an ephedra, and a grass. The prickly, thorny 
shrubs and bushes together with the cacti and yuccas are usually dis- 
posed in groups or thickets surrounded by more or less open spaces. 
In the sheltered situations are found more or less tender shrubs, grasses, 
and other herbaceous plants. 

Shrubs and grasses increase in number and variety on the foot- 
hills and there is often an abundance of shrubbery in the ravines 
near timber line. On the whole the rocky soils are much richer in plant 
food than the sandy soils because they retain moisture better. The 
desert vegetation with the exception of a few green-bark trees and 
shrubs is dull and dusty and in general the plants have pulpy leaves 
and exude gums and resins for retarding evaporation. The leaves 



LOWER COLORADO BASIN 245 

are usually small and many are covered with waterproof dermal 
structures.^ 

Under 4000 to 6000 feet the rainfall is so low and the evaporation so 
high that true desert conditions prevail. Upon the higher mountain 
slopes are limited areas where much more mesophytic conditions are 
found — less evaporation and greater precipitation ; hence islands of 
vegetation occur on the mountains surrounded by great desert plains. 
The greater portion of the area is occupied by true desert species equipped 
for life under arid conditions — structures for preventing evaporation 
and other structures for rapid absorption, great storage, and long reten- 
tion of a scanty water supply.^ The highest portion of the province lies 
in south-central Arizona, where a few mountain ranges — Baboquivari, 
Carobabi, and Cobota ranges — break the continuity of the plains. The 
Gila, MohaW'k, and Growler mountains are important ranges farther 
west. None of them has a sufficient summit extent to provoke large 
quantities of rainfall, hence even the highest portions are very scantily 
covered with tree growth. 

1 Mearns, loc. cit., pp. 32-34. 

2 D. T. Macdougal, Across Papagueria, Bull. Am. Geog. Soc, vol. 40, pp. 724-725. 



CHAPTER XVI 
ARIZONA HIGHLANDS 

Topography and Drainage 

The Arizona Highlands cross Arizona from northeast to southwest 
as a broad zone of short and nearly parallel mountain ranges separated 
by valleys deeply filled with river and lake deposits. The width of the 
zone is from 70 to 150 miles and the lengths of individual mountain 
ranges such as Santa Catalina, Pinal, Dragoon, and Ancha rarely ex- 
ceed 50 miles, while the elevations are rarely above 8000 feet. The 
northeastern portion of the Arizona Highlands is continuous with the 
ranges of the Great Basin in Nevada and Utah. On the east the com- 
mon line of division of the Arizona Highlands and the Trans-Pecos 
Highlands is roughly the Mimbres River just west of the Rio Grande. 
The ranges east of this line trend north, those west of the line trend 
northwest. Between these two divergent lines, and on the north, is the 
lava-fringed southern border of the Colorado Plateaus; on the south the 
ranges of the two provinces have no well-defined dividing line.^ 

The mountain structures are very similar to those of the Great Basin. 
They are usually monoclinal, and in the Chiricahua and Pinal ranges 
the monoclinal structure is demonstrably due to faulting as shown by 
Gilbert and by Ransome." The greater number of ranges consist mainly 
of sandstone, quartzite, and limestone (Paleozoic) that rest upon schists 
and granites (pre-Cambrian). Both types of rocks are partly covered 
by volcanic flows, Fig. 67. 

As a result of the monoclinal structure of the mountain ranges and 
the prevailing northwest strike of the beds, the southwestern slopes are 
longer and somewhat less steep than the northeastern slopes, the latter 
consisting of a series of steep scarps and benches that give the indi- 
vidual ranges notably bold mountain fronts. 

The larger creeks of the region have broad, sandy or gravelly beds of 
distinctly even gradient, and the tributaries of the main creeks exhibit 
similar features on a smaller scale. The regular gradients of the stream 

1 G. K. Gilbert, The Geology of Portions of New Mexico and Arizona, U. S. Geol. Surv. 
West of the looth Meridian (Wheeler Surveys), vol. 3, 1875, p. 508. 

2 F. L. Ransome, Globe Folio U. S. Geol. Surv. No. iii, 1904. 

246 



ARIZONA HIGHLANDS 



247 



channels and the fact that the channels are dry for the 
greater part of the year result in their use by man for 
purposes of travel and transportation; they are the 
natural roads of the region. Throughout the Arizona 
Highlands a considerable part of the small annual precipi- 
tation (15 to 20 inches and less) falls in sudden rainstorms 
or "cloud-bursts," which are common in July or August. 
The stream channels are rapidly filled with turbulent 
waters that wash along great masses of loose detritus swept 
down from the hill slopes above. The cloud-bursts are 
incredibly violent and do a remarkably large amount of 
work. It is through their energetic action that the 
mountains are dissected and the basins filled with al- 
luvium. For this reason the erosive work due to water 
action is very important in the aggregate in spite of 
the semi-arid character of the climate. 



m 



a J 



E S 



i^ 



Soils and Vegetation 

With the exception of the timbered slopes of the moun- 
tains and of the alluvial areas along the main arroyos, 
the surface of the region is almost without soil. The 
grass and shrubbery occur in such small amounts as to 
exercise but little retaining influence upon the land 
waste during short periods of heavy rainfall. Further- 
more, the deficient vegetation results in the formation 
of very small quantities of humic acid, and the rock is 
therefore not affected by such acid to anything like the 
degree to which it is affected in humid regions. The 
granitic masses crumble into particles of quartz, fragments 
of mica, and angular fragments of crystals of rather fresh 
feldspar. The quartz and mica are washed down the 
larger streams by the sudden rains; but the larger frag- 
ments of feldspar often accumulate upon the alluvial 
fans and give them a very distinctive appearance. 

The occurrence of arboreal vegetation in response to 
greater rainfall and its zonal distribution in response to 
temperature are here as everywhere in the Southwest 
interesting subjects of study. The general geographic 
distribution of the many types of vegetation has been 
worked out as follows: 



248 



FOREST PHYSIOGRAPHY 



(i) Zone of cactus, yucca, agave, scanty grass, 3000 to 3500 feet. 
More luxuriant vegetation in the vicinity of water. 

(2) Zone of Obione and Artemisia (greasewood and sage-brush), poor 
grass, diminished growth of cactus, altitude 3500-4900 feet. 

(3) Zone of cedar (Juniperus occidentalis) , few cactus, 4900 to 6800 
feet. 

(4) Zone of pine and fir, 6800 to 10,800 feet. 




Scale of Miles 



1 k i) 



X 



1 



Fig. 68. — Waste-bordered mountains of the Arizona Highlands, Camelsback quadrangle, U. S. Gaol. 
Surv. Note the lack of a permanent stream, the large number of intermittent streams as shown by 
the dotted lines, and the ragged character of the mountain slopes. Contour interval, 250 feet. 

These zones are lower on eastern and northern than on southern and 
western slopes and the amount of canting increases with increasing 
elevation (p. 293). The quaking aspen is seen below 7500 feet, likewise 
the fern {Pteris aguilina). Above 7000 feet the white oak accompanies 



ARIZONx\ HIGHLANDS 249 

the pine but is never found in great quantities, principally in small 
patches or groves. In some instances the pines occur in splendid forests.^ 

The character of the tree growth in the extreme southern part of the 
Arizona Highlands has been analysed by Mearns.- He found (1893) the 
Mexican white pine {Pinus strobiformis) at the summits of the main 
peaks of the San Luis Mountains south of the boundary line (7874 
feet); also on the Animas peaks in New Mexico (8783 feet); and in the 
San Jose Mountains (8337 feet), where a few trees grow close to the 
summit of the main peak. It is a common tree on the highest peaks 
of the Huachuca Mountains where it occupies a considerable area and 
descends as low as 6550 feet. It is an interesting fact in the distribution 
of this tree that it belongs to the Canadian life zone and is usually asso- 
ciated .wdth the Douglas spruce, aspen, etc. The yellow pine has a 
vertical range (on the Mexican line) from 6200 feet in the San Jose 
Mountains of Sonora to 8 500 feet in the Huachuca Mountains of 
Arizona. The Douglas spruce is found on the San Luis, Animas, and 
Huachuca Mountains, on all of which it reaches the summits and ex- 
tends as low as 6000 feet, in cold wxt ravines, and is not found on any 
other mountains of the boundary strip. ^ 

On the Dog Mountains in New Mexico the regular juniper zone 
extends from 6000 feet up to the summits, but in most canyons it de- 
scends to the base of the mountains. There is a well-marked juniper 
zone at 7500 feet on the west side of the San Luis Mountains also. 
The desert yucca in the fifty-mile desert west of El Paso occurs in open 
forests spread over large areas where the largest trees grow to a height 
of 16 feet. The aspen or quaking asp has a vertical range on the Mexi- 
can line from 7690 feet in the San Jose Mountains of Sonora, Mexico, to 
9472 feet in the Huachuca Mountains in Arizona. The Fremont cotton- 
wood {Populus fremontii) is the most common, beautiful, and valuable 
shade tree in the whole Mexican boundary region. It grows natu- 
rally on almost every stream along the boundary and is found planted 
around the houses and along the irrigation ditches of almost every 
ranch. In deep narrow canyons its stem is tall and slender, but in open 
spaces the isolated trees have full round tops with spreading and often 
drooping branches. The vertical range of the cottonwood is from sea 
level to 6100 feet in the Huachuca Mountains near the boundary.^ 

1 Report upon Geographical and Geological Explorations and Surveys West of the looth 
Meridian (Wheeler Surveys), Geology, vol. 3, 1875, pp. 603-604. 

2 E. A. Mearns, Mammals of the Mexican Boundary of the United States, etc.. Bull. U. S. 
Nat. Mus. No. 56, pt. i, igoy. 

3 Idem, pp. 38, 3g, 40. 
^ Idem, pp. 43-48. 



250 FOREST PHYSIOGRAPHY 

A common tree or shrub through the desert Southwest is the mes- 
quite (Prosopis glandulosa). The vertical range is from sea level and 
even below sea level in the Colorado desert up to about 5500 feet. In 
the deserts of New Mexico, Arizona, and California it is a shrub which 
obstructs drifting sand, thus forming mounds of sand and lines of sand 
hills; in the most fertile places along the Colorado River and its tribu- 
taries it is a tree of considerable size. Along the Santa Cruz River in 
Sonora are forests of unusually large mesquite, with some individuals 
2I feet in diameter and 50 feet high.^ 

The San Luis Mountains are composed largely of calcareous rock 
and are steep and rough. Where a soil covering has been formed they 
are wooded from a well-marked dry timber line at 5250 feet to the sum- 
mit at 7870 feet. Below the lower timber line the country is covered 
with grass and in places with patches of mesquite and chaparral. The 
forest trees at the lower timber line of the San Luis Mountains are 
mostly evergreen-oak (Quercus emoryi), though in the low canyons grow 
cypress, walnut, cherry, sycamore, and gray oak {Quercus gresea).^ 

The trees of the Animas Mountains (northward continuation of the 
San Luis Range) in New Mexico are the same as those of the San 
Luis, with the addition of a zone of quaking aspen. The lower timber 
line in the Animas mountains is at 5250 feet except where springs occur 
that support a belt of fine oak timber in the moist canyons far below 
the main timber line. In one instance a straggling line of oaks is ac- 
tually continuous across the valley between the Animas and San Luis 
Mountains, joining the two timber lines of these mountains down two 
long canyons.^ 

Regional Illustrations 

clifton district 

In portions of the Arizona Highlands, as for example in the vicinity 
of Clifton, near the eastern border of the state, the topography be- 
comes far less regular than is generally the case. Looking north of 
Clifton it is impossible to discern any well-defined mountain system. 
The whole region north of Gila Valley at this point appears as a maze 
of short ridges, small plateaus, and insignificant peaks. 

The topographic complexity of the highlands in the Clifton district is 
explained by the geologic structure. A core of older rocks (granites, 
limestones, and sandstones) was deeply and irregularly eroded, and at 

1 E. A. Mearns, Mammals of the Mexican Boundary of the United States, etc., Bull. U. S. 
Nat. Mus. No. 56, pt. i, 1907, pp. 59-60. 

2 Idem, pp. 89-90. 

3 Idem, p. 92. 



ARIZONA HIGHLANDS 25 1 

a later time (Tertiary) was partially covered by great masses of volcanic 
flows (rhyolites and basalts), with great variations in thickness and char- 
acter. The drainage developed upon the lavas after their extrusion, 
was consequent upon the lava flows; those portions of the region not 
affected by lava flows preserved their original drainage. The conse- 
quence was that extremely irregular drainage courses were made still 
more irregular by the differences in hardness between flat-lying basalt 
and deformed rock of older age.^ The only regular features of the 
Clifton district are the small plateaus due to volcanic accumulations or 
to the regular and broad uplift of sedimentary rock; but even these 
plateaus are but dimly discerned and all of them are deeply dissected 
by canyons and furrowed by a maze of shallow and wide-spreading 
ravines. 

The arboreal vegetation of the Clifton district is found at elevations 
above 6000 feet, though below this elevation the ridges generally sup- 
port a certain amount of agave, yucca, and low cactus. Above the 6000- 
foot level stunted juniper and cedar are quite common and are used 
as firewood; on the higher slopes a growth of manzanita bushes and 
stunted oak is also found. The heaviest timber grows in the sheltered 
mountain basins at altitudes of 5000 to 6000 feet and consists largely 
of yellow pine. Along some of the river bottoms are large groves 
of Cottonwood. Many of the dry mountain spurs are covered with 
pinon and juniper.^ 

BRADSHAW MOUNTAINS 

The higher peaks of the Bradshaw Mountains district are composed of 
gneiss, granite, and schist, the granite having been intruded into the 
schists. Differential erosion has resulted in a high relief, due to the 
more resistant character of the intrusive granite. In some places, 
quartzite ■ combs in the granite stand prominently above the general 
level of the wide valleys formed upon the less resistant schist and may 
be traced for miles by their distinctive and bold relief. 

Toward the northwest the Arizona Highlands are also marked by a 
large number of rather extensive lava flows which have covered over 
the older topography and simplified the contour of the surface. Among 
them is Black Mesa, 10 miles east of the Bradshaw Mountains, 
Bigbug Mesa, 15 miles northwest of Black Mesa, and many others 
of lesser extent. They are striking forms, for they lie in a region 
of generally rugged topography whose irregularities have been devel- 

1 Waldemar and Lindgren, Clifton Folio U. S. Geol. Surv. No. 129, 1905, p. i. 

2 Idem, p. 2. 



252 



FOREST PHYSIOGRAPHY 



oped upon rocks of complicated structure and variable hardness. They 
are almost without soil, since they consist of durable basalt recently 
formed. The basalt weathers into spheroidal fragments of variable size 
which cover the surface and make the so-called "malpais" of the region. 
Between the fragments finer waste accumulates in small quantities and 
supports a thin growth of grass in the rainy season. 

The schists of the district weather very slowly and their soils are thin, 
so that the outcrops of the steeply inclined or vertical strata are visible 



»^|^»~"»!».»^aa 




Fig. 69. — Bradshaw Mountains, looking northwest near Goddard. The mountains are composed of 
granite; the plain in foreground is underlain by basaltic agglomerate. (U. S. Geol. Surv.) 

for miles. The quartz-diorite and granite weather more rapidly and are 
covered with a sandy soil which supports a good forest growth in the 
higher mountains of the region toward the north. The quartz-diorite 
weathers most easily of all and is noted for the characteristic basin or 
park-like forms developed upon its outcrops. 

The semi-aridity of the plains and valleys of this district has resulted 
in the development of a characteristic arid vegetation. The common 
vegetation of the lower slopes consists of cactus, yucca, maguey, 
paloverde, "cat claw," etc. In favored iocahties there are stunted 
growths of oak and manzanita, and in the arroyos one may find larger 
oaks and sycamores in some quantities. On the mountains where 
greater rainfall is precipitated on account of the greater elevation pine 
and fir find a congenial habitat. 



ARIZONA HIGHLANDS 253 

In the Bradshaw Mountains the precipitation is greater than on the 
surrounding plains. Heavy thunder showers occur almost daily in 
July and August, and during the winter months the mountains are fre- 
quently covered with snow. The hea\dest timber grows in the moun- 
tain basins at 5000 and 6000 feet and is largely yellow pine and its varie- 
ties. Some of the river bottoms have by contrast thickets of willow, 
mesquite, and alder, and groves of cottonwood, while the mountain spurs 
are frequently covered with thick mats of shrubs or dense stands of pin 
oak, nut pine, greasewood, and juniper.^ 

SANTA CATALINA MOUNTAINS 

The Santa Catalina Mountains ten or twelve miles north of Tucson 
are among the most impressive ranges of the province and indeed of the 
Southwest. Their deeply dissected, bold, picturesque slopes rise to a 
series of exceptionally ragged peaks. Perpendicular cliffs and sharp 
ridges are common, among them "The Needles," a series of long slender 
precipitous points which crown the summit of a sharp granite ridge that 
rises 3000 feet above the plain at the mountain base. The highest 
point in the range is Mount Lemmon, which rises to 10,000 feet, or 7000 
feet above the plains. The ranges composing these mountains are sub- 
parallel, extend nearly east-west, and the whole belt is about 50 miles 
long and almost as wide. The southern slope is especially rugged, so 
that even the cacti, hardy yuccas, and Spanish daggers have a hard 
struggle to maintain themselves on the barren rocks. Oaks and juniper 
are occasionally found in some sheltered alcove, and the summits of the 
higher mountains and large portions of the northern slopes are covered 
with pine and fir.- 

Eastern Border Features 

The northeastern edge of the Arizona Highlands is formed by the 
Grand Wash cliffs and their continuation — the Yampai Chffs — which 
rise in a precipitous manner 4000 feet or more above the plains that on 
the north stretch westward from their base, Fig. 67. The continuity of 
the westward-facing escarpment is broken by several canyons. Here in 
a few places the confluent alluvial fans constitute a piedmont foreland 
of slight development. The lower portion of the cliffs is steep but not 
even approximately perpendicular. It is composed of granite, while the 
upper portion of the slope is of limestone and decidedly precipitous. 

In the northern portion of the Arizona Highlands and in the Sacra- 

1 Jaggar and Palache, Bradshaw Mountains Folio U. S. Geol. Surv. No. 126, 1905, p. i. 

2 J. W. Toumey, La Ventana, Appalachia, vol. 8, 1897, pp. 225-232. 



254 FOREST PHYSIOGRAPHY 

mento Valley region in northwestern Arizona the mountain escarp- 
ments face the plateau and are due to faulting. Specific localities are 
Globe, Arizona, and the mouth of the Grand Canyon. Farther from the 
edge of the plateau sedimentary rocks do not occur in many cases, and 
it is difficult to tell whether the mountains, composed of crystalline rock, 
are the products of local uplift or of circumdenudation. In general the 
mountains parallel the bordering plateau and become smaller and more 
isolated the greater their distance from the plateau. As the mountains 
grow less conspicuous the valleys broaden to greater and greater width 
and finally blend into each other in such a manner as to form a plain 
completely surrounding isolated mountain groups. The topographic 
character of this portion of Arizona lies between two extremes of well- 
defined fault-block mountains and narrow gorge-like valleys near the 
Colorado Plateaus and broad alluvial plains surrounding single' mountain 
groups at a distance from the plateau. 

Truxton Plateau serves as a type of the eastern border features. It 
is comparatively level and extends from the Yampai cliffs on the east to 
the Cottonwood and Aquarius cliffs on the west. It lies about 5000 
feet above the sea and consists of denuded granite whose depressions 
have been almost filled with eruptive rock but whose higher portions 
project above the lava. Truxton Plateau is described as a lava- 
covered peneplain which has been slightly dissected by a few streams 
that have cut narrow canyons.^ The recent uplift of Truxton Plateau 
is indicated by the rapid deepening of the stream valleys as they 
approach the cliffs to the west, while their courses within the plateau 
are distinctly shallow.- 

For general remarks on Soil Investigations and the Soils of New Mexico and Arizona see 
G. K. Gilbert, U. S. Geol. Surv. West of the looth Meridian (Wheeler Surveys), vol. 3, 1875, 
pp. 594-597. For climatic conditions, idem, pp. 598 et seq. Also idem, pp. 603 et seq., for the 
geographical distribution of plants in this region. 

Rainfall and Rings or Growth 

The conditions of growth of the forests of yellow pine in the northern 
Arizona region have suggested that they might form climatic registers of 
great importance and that a study of the rings of growth may indicate 
the character of the climate during the life of the individual tree. This 
matter has recently been studied with some very interesting results.^ 

1 W. T. Lee, A Geologic Reconnaissance of a Part of Western Arizona, Bull. U. S. Geol. 
Surv. No. 352, 1909, p. 21. 

2 For a brief discussion of the physiography of Arizona and the topography of the Globe 
quadrangle with some excellent cross sections see F. L. Ransome, The Geology of the Globe 
Copper District, Arizona, Prof. Paper U. S. Geol. Surv. No. 12, 1903. 

3 A. E. Douglass, Weather Cycles in the Growth of Big Trees, Weather Rev., June, 1909, 
pp. 225-237. 



ARIZONA HIGPILANDS 255 

It has been shown that at the 7000-foot elevation at which these trees 
grow the seasons are very sharply defined; the mean temperature for 
January is 29°, that for July 65°. Consequently there is a sharply 
seasonal character to the tree growth. A narrow red ring is formed 
during the autumn and winter and a broad, soft, white ring during 
the summer. Under the microscope the winter cells look lean and 
emaciated; the summer cells are round and well fed. The winter ring 
is thin, hard, and pitchy; the summer ring is wide, white, and pulpy. It 
appears probable that the red winter rings are governed directly by 
the low temperature and the white summer rings by the abundance of 
moisture. 

About twenty sections have been measured by micrometer scale and 
the result is thousands of readings covering a period of from two to five 
centuries. On theoretical grounds it would seem that these rings of 
growth ought to register the rainfall, for they are a measure of the food 
supply, which depends entirely upon moisture, especially where the 
supply is limited and the life struggle of the tree is against drought and 
not against its fellows or members of other species. The measurements 
show that the rainfall curves and curves of growth have a really remark- 
able resemblance. An analysis of the curves of growth for longer 
periods during the life of the tree indicates that there is a direct con- 
nection between curves of growth and curves of rainfall in 21.2 and 32.8 
year periods^ with suggestions of shorter periods, especially in the case of 
the ii-year period already determined by Bigelow.^ 

1 E. Bruckner (Vienna), Klimaschwankungen seit 1700, nebst Bemerkungen iiber die 
Klimaschwankungen der Diluvialzeit, 1890. In this paper the author assembles the data 
for the changing level of the Caspian Sea and its tributaries to show a strikingly regular rise 
and fall in cycles of about 35 years. Further investigations by Briickner show that these 
oscillations hold for much larger areas than the Caspian region, probably for the whole world. 
Still later analyses of rainfall curves in numerous localities have brought out the generality of 
this fact and the wide application of the law of climatic oscillations. 

- F. H. Bigelow, Studies of the Diurnal Periods in the Lower Strata of the Atmosphere, 
Weather Rev., July, 1905. 



CHAPTER XVII 

COLORADO PLATEAUS 

The physiographic province known as the Colorado Plateaus is 
roughly circular in shape and embraces portions of the states of Utah, 
Arizona, Colorado, and New Mexico. The Grand Wash Cliffs on the west, 
the Uinta Mountains on the north, the Colorado ranges and the Trans- 
Pecos Highlands on the east, and the Arizona Highlands on the south 
are the most conspicuous border features. The boundaries are definite 
on the west, north, and south, but the eastern boundary is in many 
places indefinite, partly because of its topographic character, partly be- 
cause it is the least-known portion. The outline displayed on the gen- 
eral physiographic map, Plate II, follows rather closely that assigned by 
Button.^ 

Its most prominent and general characteristics are (i) the fiat and 
but partially dissected upper surfaces of the various members of the 
province; (2) the distinct boundaries of the individual members as 
determined by (a) strongly developed, northward- trending fault scarps 
and (b) eastward-trending lines of cliffs developed most strikingly upon 
the out-cropping strata of the High Plateaus of Utah; and (3) the great 
canyons that ramify through almost every large section but are thoroughly 
developed in the central portion. The most striking physiographic 
features of the province are the Colorado River and its world-famous 
canyon. An early view of the course of the river ascribed its origin 
to a great fault which the river followed and modified. The detailed 
studies of later years show that certain portions of it are demonstrably 
located upon faults but that the course as a whole is independent of 
faulting; and the facts as at present known point to a consequent origin 
upon either (i) the deformed surface of a peneplain or (2) the present 
structural surface when it was in a different attitude.^ 

While the surfaces of the individual members of the Colorado Plateaus 
are smooth or gently undulating, level or slightly tilted, and so undis- 

1 C. E. Dutton, Mount Taylor and the Zuiii Plateau, 6th Ann. Rept. U. S. Geol. Surv., 
1884-1885, pp. 114-117, and Plates 11 and 12. 

2 H. H. Robinson, The Tertiary Peneplain of the Plateau District and the Adjacent Coun- 
try in Arizona and New Mexico, Am. Jour. Sci., vol. 24, 1907, p. 129. 

256 



(COL( 



L.L.|P0ATES, ENG. CO. 



PLATE II 




Plate II. — Colorado Plateaus. 



COLORADO PLATEAUS 



257 



sected as a whole that 
the level sky line, the 
broad expanse, the 
great extent of struc- 
tural surface are among 
the most important 
elements of the relief, 
yet it must not be 
thought that the region 
can be described even 
in general phrase as 
level. The great depth 
to which the canyons 
have been cut and the 
great breadth to wliich 
they have been widened 
by the action of sec- 
ondary erosional pro- 
cesses have resulted in 
strong relief so that 
the province is one of 
the ruggedest in the 
West. UnHke the 
mountain sections of 
the West its relief is 
not to any important 
degree the product of 
upward departures from 
the general level of the 
region but of down- 
ward departures. In- 
stead of mountain 
flanks we have here 
prodigious canyon walls 
diversified by innumer- 
able cliffs; instead of 
lofty ridges and peaks 
we have here profound 
chasms. Exceptions to 
this rule are the vol- 
canic and laccolithic 




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§.2 




258 FOREST PHYSIOGRAPHY 

masses that rise above the general level to a truly mountainous height, 
such as Mount Taylor (southeast), the San Francisco Mountains (San 
Francisco Plateau), Mount Dellenbaugh (Shiwits Plateau), Mounts 
Trumbull and -Emma (Uinkaret Plateau), and the Ute Mountains of 
southwestern Colorado, Fig. 70. They are not in the aggregate of 
great extent, but they are important not only through their relief 
but also through their , association with those great lava sheets that 
although greatly eroded still cover large portions of the Colorado 
Plateaus. 

It is important to see at the outset that the degree of dissection 
of the different portions of the province is not everywhere the same. 
The San Francisco Plateau is so little dissected that within its margins 
there is little hint of the great erosion forms to be found elsewhere 
in the region, and the flat plateau quality comes out strikingly" in every 
general view; on the other hand the northeastern, north-central, and 
central portions of the province are dissected by a maze of ramifying 
canyons. The great breadth of the canyons m this portion of the 
province might be made the basis for a separate division of the pla- 
teau country — the Canyon Lands, as Powell termed the large dis- 
trict included in the valleys of the upper Colorado and the lower 
Green and Grand. ^ So thoroughly dissected is this portion that 
the walls of the labyrinthine canyons are the dominating elements 
of the relief, and movement across the country is by tortuous and 
extremely toilsome routes, now paralleling some small stream in 
the depths of a profound abyss, now crossing a plateau spur of 
mountainous proportions. The degree of topographic development 
which each district has attained will be the subject of further dis- 
cussion; here it is sufficient to note that although the strata in 
their horizontal development are decidedly uniform over the whole 
area, the topographic aspects of the various sections are as decidedly 
variable. 

A special feature of the plateau country is the manner in which ero- 
sion takes place. It is directed against the almost vertical edges of the 
strata much more than upon the almost flat upper surfaces. Plateau 
erosion is by stripping through cliff recession. Wash is almost ineffec- 
tive on the flat gradients of the plateau summits; on the steep and 
alternating slopes and cliffs of canyons and the cliffed edges of out- 
cropping strata everywhere it is vigorous, as is suggested by the name 
" Colorado," whose colored, turbid current carries the waste of its 

. ^ J. W. Powell, Lands of the Arid Region of the United States, U. S. Geog. and Geol. Surv. 
of the Rocky Mountain Region, 1879, p. 105. 



COLORADO PLATEAUS 



259 



great tributary system of 
cliffs and slopes with their 
streams of land waste.^ 

With this special erosion 
feature in mind it will be easy 
to understand how extensive 
the canyon systems of the 
plateau and the associated 
terraces are, and yet how 
within the borders of each 
plateau there is in many 
cases so little dissection; each 
plateau is attacked prac- 
tically on its margins only 
and so preserves almost until 
extinction a marked summit 
flatness. Conversely we 
should not understand be- 
cause such large expanses of 
flat plateau exist, and each 
is so little dissected within 
its borders, that erosion of 
the general surface is not 
active, for in the province as 
a whole, and between the 
fiat-topped plateaus, erosion 
is taking place at a most 
rapid rate. 

The Colorado Plateaus 
consist of a large number 
of individual members sepa- 
rated from each other in 
various ways but in most 
cases by strongly defined 
lines, Plate II. The most 
striking line of division is 
the Colorado Canyon itself, 
which separates a northern 

1 For a discussion of erosion by clifl 
recession see J. W. Powell's various 
reports on the Colorado Plateaus. 



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26o FOREST PHYSIOGRAPHY 

from a southern series. Crossing the canyon almost at right angles are 
a number of northward-trending faults and associated fault scarps 
which block out an east-west series of plateaus. A third type of pla- 
teau boundary is exhibited in central Utah where the worn edges of 
outcropping, northward-dipping plateau strata constitute a line of 
remarkable cliffs of great physiographic interest and unusual scenic 
beauty. Besides these well-marked divisions are others of lesser defi- 
nition. The northeastern and southeastern sections, although of great 
extent, have never been studied in the same detail as the rest of the 
plateau province, and their mutual boundaries are therefore less defi- 
nitely established. They are roughly separated irom the other divisions 
by the Green-Colorado Valley on the northwest and the Little Colorado 
on the southwest, and from each other by the valley of the San Juan. 
The various lines of division block out four large and important districts 
or sub-provinces, a fact that needs emphasis, for the elementary student 
usually regards the great plateaus north of the canyon and in the Kaibab 
district as the only important parts of the province. The separate 
districts may be called for convenience: 

I High Plateaus of Utah: Awapa, Aquarius, Paria, Kaiparowits, 
Markagunt, Paunsagunt, Tushar, Wasatch, Sevier, Fish Lake, etc. 
II Grand Canyon District: Shiwits, Uinkaret, Kanab, Kaibab, San 
Francisco, Coconino, etc. 

III Southern District: Zuni, Natanes, Taylor, etc. 

IV Grand River District: White River, Roan or Book, Uncom- 
pahgre, Dolores, etc. 

High Plateaus of Utah 

In any general view of the plateau country, as shown in Plate II, 
two distinctly different scarp systems may be seen. The north-south 
system as just described is caused by great faults with downthrow on 
the west. Almost equal to the north-south system of escarpments in 
magnitude is the east-west system that crosses the plateau country 
several hundred miles north of the Grand Canyon, a system due to 
plateau stripping, each cliff marking the outcrop of a resistant stratum. 
The individual scarps of the latter system break the northward conti- 
nuity of the Colorado Plateaus in a most decided manner and block 
out the country into a series of north-south plateaus, among which are 
the Colob, Markagunt, and others, the whole series known as the High 
Plateaus of Utah.^ They are all characterized by great ruggedness of 

1 C. E. Button, The Tertiary History of the Grand Canyon District and Geology of the 
High Plateaus of Utah, Mon. U. S. Geol. Surv., vol. 2, 1882. 



COLORADO PLATEAUS 261 

outline, pronounced declivity, and a rude parallelism, although they are 
most irregular in detail. Named in order from south to north the prin- 
cipal ones are the Shinarump Cliffs, Vermilion Cliffs, White Cliffs, and 
Pink Cliffs, while many lesser cliffs block out plateaus of smaller extent. 

The cliffs and intervening plateaus constitute a group of great terraces 
from 30 to 40 miles in extent north and south and 100 miles east and 
west. Among the great cliffs perhaps the most remarkable in form are 
the White Cliffs, while among the most remarkable in color are the 
Vermilion Cliffs. The latter are from 1000 to 2000 feet high, more 
than 100 miles long, and consist of evenly stratified layers of sandstone 
and shale with gypsiferous partings. In color they are brick red, which 
at twilight takes a strong vermilion hue; in form they are very ornate 
and architectural, with many vertical ledges rising tier above tier with 
intervening talus slopes through which the fretted edges of the cliffs pro- 
ject.^ Though the profile is complex it never loses its typical character 
and is always extremely picturesque because of the numberless alcoves 
and alternating promontories where streams cut into the edges of the 
plateaus which these cliffs terminate. 

The escarpments of the northern plateau country are all of a different 
type from those to the south. They consist of the outcropping edges 
of resistant northward-dipping strata that act as cliff makers and are 
being slowly stripped off the plateau surface by wind and water erosion. 
The former greater extent of the strata is inferred from the remnants 
left out upon the surface of the plateau south of the main cliffs in the 
form of isolated buttes and mesas. The map abounds in illustrations, 
of which perhaps the most conspicuous are the mesas that occur south 
of the Virgin River and west of Canyon Spring. 

In general the drainage of the region in which the east-west line of 
great cliffs occurs is from the north southward, and it is therefore in this 
direction that the main canyons run in contrast to the east-west course 
of the Grand Canyon farther south. There are three principal streams 
in this district: the Virgin flows west to the Great Basin and finally to 
the Colorado; Kanab Creek flows southward through a deep narrow 
gorge to enter the Colorado midway of the Kanab Plateau; and Paria 
River enters the Colorado at the head of the Marble Canyon. The 
beds of the plateau streams retain pools of water in the depressions pro- 
vided they are flooded with material that is not too coarse. These pools 
are called "water pockets," "lakes," "pools," or "tanks." They are 
scattered and few in number though always important features of the 

I C. E. Dutton. Tertiary History of the Grand Canyon District, Mon. U. S. Geol. Surv. 
vol. 2, 1882, pp. 17, 52, 53. 



262 



FOREST PHYSIOGRAPHY 



whole region. They are much more numerous in the higher plateaus of 
Utah than in the lower country. They are an important source of supply 
for travelers, settlers, and stockmen, and are the resort of bands of wild 
horses that roam the uninhabited desert tracts. 

The High Plateaus consist of three principal members, a western, a 
central, and an eastern, Fig. 72. The western member is composed of the 




Fig. 72. — Principal relief features of the High Plateaus of Utah. For Colb, lower left-hand corner, 
read Colob. Scale, 30 miles to the inch. (Button, U. S. Geol. Surv.) 



Pavant, Tushar, and Markagunt plateaus, named in order from north 
to south; the central member is composed of the Sevier and Paunsagunt 
plateaus, named in the same order; and the eastern member consists 
of the Wasatch, Fish Lake, Awapa, and Aquarius plateaus. 



COLORADO PLATEAUS 263 

We shall describe only a few of the great plateaus of this northern 
region, selecting those which from our standpoint appear most impor- 
tant as types in the series. 

AQUARIUS PLATEAU 

The Aquarius, the grandest of all the High Plateaus, is about 35 miles 
long, of variable width, and 11,600 feet high. Its summit is clad with 
dense spruce forests sprinkled with grassy parks and exceptionally 
beautiful lakes. ^ These are not small pools but broad sheets of water 
from I to 2 miles long. Their existence is due to differential erosion by 
local glaciers that originated in the higher portions of the plateau; 
8500 to 9000 feet was the lower elevation of the glaciers of the region 
and it is at this level that the terminal moraines are usually found. The 
high elevation of the Aquarius Plateau, 10,500 to 11,600 feet, favored 
the exceptional development of glacial forms in the Pleistocene, just as 
to-day it favors a greater rainfall and better forest cover than occur on 
the neighboring lower plateaus. 

The upper surface of the Aquarius is developed upon a 1000- to 2000- 
foot layer of basalt, which gives rise to marginal cliffs of exceptional 
height and steepness, as on the northwestern flank. Again, on the eastern 
border, a great wall from 5500 to 6000 feet high overlooks the lower coun- 
try and owes its boldness largely to the hard lava cap at the summit." 

A WAP A PLATEAU 

The Awapa Plateau is 35 miles long and about 18 miles broad; its ele- 
vation is about 9000 feet. The western border of the plateau is a wall 
from 1800 to 3000 feet high, but the other boundaries are less distinct. 
The slopes of the surface everywhere converge toward a central de- 
pression. Rabbit Valley. Although its altitude is that at which moisture 
and vegetation usually occur, only sage-brush and grasses grow and not 
a spring or a stream is found upon its entire surface. It is an endless 
succession of hills and valleys and shallow canyons (400 to 500 feet). 
It consists entirely of a great variety of volcanic material which has 
been poured out upon a sedimentary base or platform. Some of the 
grandest and most massive trachytic beds of the plateau region are 
found here. The irregular distribution and varied dissection of the 
many kinds of lavas that occur upon it are in large part the cause of 
the irregular relief of the surface.^ 

1 C. E. Button, Geology of the High Plateaus of Utah, U. S. Geog. and Geol. Surv. of the 
Rocky Mountain Region, 1880, p. 5. 

2 Idem, pp. 292-293. 

3 Idem, pp. 272-276. 



264 FOREST PHYSIOGRAPHY 

PARIA PLATEAU 

The Paria Plateau terminates on the south in a semicircular line of 
cliffs which are really a great southward prolongation of the Vermilion 
Cliffs and include the same strata (Triassic). It lies almost in line with 
the great Kaibab series of plateaus, yet topographically it is a part of 
the High Plateaus of Utah and like them is a great structural terrace. 
It is scored by a labyrinth of sharp narrow canyons which cut deeply 
into the platform-like surface. The course of the main drainage fea- 
ture, the Paria River, is independent of the dip of the strata; the courses 
of the smaller streams are all dependent upon the structural dips.^ 
Only the channel of the Paria, however, carries water. The rest are all 
dry channels which appear to have been formed during the moister 
glacial period and to have become functionless with the adyent of the 
drier postglacial climate. Growing aridity has extinguished the smaller 
streams and increased the area drained by the living streams.^ 

KAIPAROWITS PLATEAU 

Between the Henry Mountains and the Paria Plateau, Plate II, is a 
broad area of plateau and canyon country known as the Kaiparowits 
Plateau and the Escalante Canyon. The canyons of both the Escalante 
and its numerous tributaries are a network of deep narrow chasms 
hemmed in by great unscalable cliffs. The depression carved by these 
streams is bordered on the north and west by a line of cliffs which ter- 
minate the Aquarius and Kaiparowits plateaus respectively. The Aqua- 
rius Plateau is forest clothed because high and relatively well watered; 
the Kaiparowits Plateau has only a scattered tree growth of very limited 
development; the depression below them on the southeast is waterless 
and treeless — a desert country, swept bare of soil. The cliffs which 
border the Kaiparowits Plateau on the northeast are 60 miles long and 
almost 2000 feet high. Their summit constitutes a divide from which 
almost no streams descend to the barren country below them on the 
east and only a few traverse the gentler western slope. 

MARKAGUNT PLATEAU 

The Markagunt Plateau, Plate II, is a broad plateau expanse south 
of the Tushar Plateau. It is limited on the west by the Hurricane fault 
scarp ; the eastern base lies at the foot of the great Sevier fault on whose 

1 C. E. Button, Tertiary History of the Grand Canyon District, Mon. U. S. Geol. Surv., 
vol. 2, 1882, p. 201. 

2 Idem, p. 202. 



COLORADO PLATEAUS 265 

eastern side the Paunsagunt Plateau is found. The greater part of 
the area is covered with eruptive rock (trachyte) resting on sedimen- 
taries (Tertiary). The southern margin is a line of cliffs not made 
by faulting but by erosion of hard cliff makers in the northward-diJD- 
ping series that constitutes the High Plateaus of Utah. The surface 
of the Markagunt consists of rolling hills and ridges and grassy slopes, 
the greater part covered with scattered groves of pine. Few canyons 
are sunk below its general level.^ 

PAUNSAGUNT PLATEAU 

The Paunsagunt Plateau is the southernmost extension of the High 
Plateaus of Utah and fronts south, with a marginal line of cliffs like its 
neighbors both east and west. These are the Pink Cliffs, often resembling 
in a most striking way well-known architectural forms such as ruined 
colonnades, buttresses, and panels. Its strata are sensibly flat and are 
wholly of sedimentary origin, not volcanic flows capping sedimentaries 
as is the case with so many of the plateaus of this region.^ 

TUSHAR PLATEAU 

The Tushar Plateau is highly inclined and is a transition type be- 
tween the flat plateaus general to the Colorado Plateaus province and 
the fault-block mountain type of the Great Basin. It is transitional in 
position as well as topography and structure, and, strictly speaking, lies 
within the geographic limits of the Great Basin. Its eastern front is 
steep and mountainous, for it has been developed largely across the 
edges of the strata; the v/estern slope is down the dip of the strata and 
though considerably dissected is far less bold. Its summit is crowned 
by a cluster of peaks, true erosion remnants, which reach above timber 
line.^ 

WASATCH MOUNTAINS 

Although the Wasatch Mountains are not a part of the High Plateaus 
they are in such close relation to them as to demand a word of expla- 
nation at this point. They stand as a great wall upon the northwestern 
margin of the plateau country overlooking the Great Basin, and con- 
sist of a number of abrupt ranges crowned with sharp peaks that attain 
altitudes of 10,000 to 12,000 feet. Their boldness gives rise to a mod- 
erately heavy rainfall, and the mountain slopes bear forests of spruce, 
pine, and fir, while the broken and drier foothills support a growth of 

1 C. E. Button, Geology of the High Plateaus of Utah, U. S. Geol. Surv., 1S80, pp. 195 
et seq. 

2 Idem, pp. 251 et al. 
' Idem, p. 173. 



266 



FOREST PHYSIOGRAPHY 




PORTION OF SALT LAKE QUADRANGLE, UTAH 

Showing (listributiou of glacial formations 

Scale of Miles 

1 2 I G 8 10 12 

Contour interval 1000 feet 



Fig- 73- — Former glacier systems of the Wasatch Mountains. (After Atwood, U. S. Geol. Surv.) 



pinon pine and cedar. In the valleys there are many natural meadows 
but no forest growth, merely groves of aspen about the springs and 
lines of willow, box elder, and Cottonwood on the borders of the 
streams.^ 

The Wasatch Mountains extend about loo miles south of the meeting 
point with the Uintas, or about to Mount Nebo, 75 miles south of 

1 J. W. Powell, Lands of the Arid Region of the United States, U. S. Geog. and Geol. 
Surv., 1879, p. 96. 



COLORADO PLATEAUS 



267 



Great Salt Lake. Beyond this point the western margin of the plateau 
country is the western edge of the High Plateaus. These in turn give 
way to the broad platform of Carboniferous rock that constitutes the 
surface of the Grand Canyon District, whose western margin is the 
Grand Wash Cliffs. The eastern slope of the Wasatch Mountains falls 
off gradually as a 15 to 20 mile belt of broad ridges and mountain 
valleys whose waters reach Great Salt Lake through gorges that cut 
across the main western range of the mountains. The gentler eastern 
slopes are generally well clothed with vegetation. On the west the 
mountains present a bold abrupt escarpment which rises suddenly 
out of the broad fiat plains of the Utah basin. The degree of abrupt- 
ness may be appreciated from the fact that the mountains attain 
elevations of 10,000 feet within i or 2 miles of the western base.^ 

The main crest of the Wasatch Mountains is near the eastern border 
of the range and the western valleys are therefore much longer than 
the eastern valleys, — generally from two to three times as long. The 
loftier peaks — -11,000 to 12,000 feet — that are developed upon crys- 
talline or highly metamorphic rock have rugged, pinnacle-like forms, 
those developed upon horizontal sedimentary beds have pyramidal out- 
lines with alternating cliffs and talus slopes. 
In both cases the sharpness of form is due 
to glaciation. Summits that do not reach 
above 9000 feet, and hence were never glaci- 
ated, are rounded and softened and bear a 
heavy cover of land w^aste. 

The elevation necessary for the development 
of Pleistocene glacier in the Wasatch Moun- 
tains was 8000 to 9000 feet. Over 50 glaciers 
were formed exceeding a mile in length. Of 
these, 46 were west of the crest, and but 4 
east of it. Of the 10 exceeding 5 miles in 
length, 9 lay on the western slope, i on the 
eastern. The greater number and size of the 
western glaciers were determined by the larger 
catchment areas and by the heavier snowfall, 
the west slope being the windward or exposed slope. The western val- 
leys were therefore more completely cleared of loose material, the ex- 
posed surfaces more rounded, the main canyons deepened by a greater 
amount, and more massive moraines developed than in the eastern 
valleys. The typical relations of the moraines to each other and to 

I S. F. Emmons, U. S. Geol. Expl. of the 40th Parallel (King Surveys), vol. 2, 1877, p. 340. 



i 


\< 


k 


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m 






FAULT' 


"'-a 






11 


f 


FAULT 


, " ,\i 




"'■""^ 




'I 


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Hoxalnes of later V 
epoch 

Fig. 74. — Sketch map of morainic 
ridges near the mouth of Bell 
Canyon, Wasatch Mountains. 
(Atwood, U. S. Geol. Surv.) 



268 



FOREST PHYSIOGRAPHY 



the drainage features in a single valley are shown in Fig. 74. The ex- 
tent of the glacial systems and their relation to the topography and 
drainage are shown in Fig. 73.^ 

Grand Canyon District 

The most celebrated and best-known portion of the Colorado Pla' 
teaus is the Grand Canyon district. The great north-south crustal 
fractures of this part of the plateau region are lines of faulting which 
block out the separate members of the district. Named in order from 
west to east the plateaus are the Shiwits, Uinkaret, Kanab, and 
Kaibab. Their elevations increase in the same order: the Shiwits is 




1 n 
_Vernnilion CI. shinarump CI. 



Grand Canyon 



Kg- 7S- — East-west (top) and north-south (bottom) sections of the Colorado Plateaus, Grand Canyon 
district, showing both structure and topography. G.W., Grand Wash Cliffs; H., Hurricane Ledge; 
T., Toroweap fault scarp; W.K., West Kaibab fault; E.K., East Kaibab monocline; E., Echo Cliffs 
and monocline. (Davis, Bull. Mus. Comp. Zool., modified from Dutton.) 



5000 feet and the Kaibab, the highest of all, is 8000 to 9000 feet above 
the sea. These several plateaus lie on the northern margin of the 
Grand and Marble canyons and constitute in the aggregate a great plat- 
form of nearly horizontal strata (Carboniferous) which is bounded on 
the east and north by the cliffs of the High Plateaus developed upon 
younger strata (Mesozoic) and on the west and south by its own termi- 
nal escarpment that descends to the older rock (Silurian and Archaean) 
of the Great Basin and Arizona Highlands.- 

The elevations of all the plateaus except the Kaibab are not great 
enough to cause a precipitation adequate for a forest growth. In con- 
trast to the hot, dreary, and barren plateaus about it the Kaibab pla- 
teau is moist, and bears meadows and parks and forests of spruce and 
pine. The descent from one flat-topped plateau to another is over a 

1 W. W. Atwood, Glaciation of the Uinta and Wasatch Mountains, Prof. Paper U. S. 
Gaol. Surv. No. 6i, 1909, pp. 73-93. 

2 C. E. Dutton, Tertiary History of the Grand Canyon District, Mon. U. S. Geol. Surv., 
vol. 2, 1882, p. 19. 



COLORADO PLATEAUS 269 

high, ragged, westward-facing clifif whose front is constantly battered 
back by wind and rain. The cHffs are great fault scarps which are 
strikingly linear and continuous. They are of such prominence as to 
cause a local rainfall which concentrates the erosive work of the 
running water; detrital material, due to cliff recession principally, is 
washed forward from the foot of each cliff in the form of long, slop- 
ing, waste fans. The cliffs retreat without being obliterated, in part 
because of the horizontally bedded rocks, in part because of their recent 
origin and the small rainfall of the region. 

SHIWITS PLATEAU 

The Grand Wash Cliffs are the westernmost of the series in the 
Grand Canyon district and form the western border of the Shiwits 
Plateau. They are from 1000 to 2000 feet high and overlook the 
Grand Wash and Huaipi valleys and the rugged sierras and stern 
deserts of the Great Basin. They form a continuous and bold line of 
cliffs from the upper Virgin Valley southward across the Colorado 
River almost 150 miles, to Music Mountain, where they are replaced 
by the Cottonwood and Yampai Cliffs. There is no river along 
this western wall of the plateau, "only occasional deluges of mud, 
whenever the storms from the southwest are flung against the lofty 
battlements and break in torrents of winter rain." ^ The Grand Wash 
Cliffs mark the western end of the Colorado Canyon, 5000 feet 
deep ; toward the west the Colorado suddenly changes its character and 
continues seaward without extraordinary features. Eastward of the 
Grand Wash Cliffs but still on the western border of the Shiwits 
Plateau is a second line of cliffs similar to the Grand Wash Cliffs in 
form but not in origin. It represents merely the eroded upper layers of 
the geologic series exposed by faulting and pushed back by ordinary 
erosion to their present position. 

The surface of the Shiwits Plateau is diversified by a number of vol- 
canic masses and a few large mesas and buttes, outliers of higher strata 
capped and so preserved by basalt. The most conspicuous height is 
Mount Dellenbaugh, 6750 feet high, a central mass of basalt in a large 
basaltic field.- 

TJINKARET PLATEAU 

The Uinkaret Plateau, nexi east of the Shiwits, is separated from the 
latter by Hurricane Ledge, a fault scarp 1000 feet high which is con- 

1 C. E. Button, Tertiary History of the Grand Canyon District, Men. U. S. Geol. Surv., 
vol. 2, 1882, p. 12. 

2 Idem. 



270 FOREST PHYSIOGRAPHY 

tinued south of the Canyon by the Aubrey CHffs, of similar height and 
origin.^ 

The Uinkaret Plateau is the narrowest of the four and its southern 
portion is the most strongly diversified by basaltic eruptions. In- 
deed this portion (20 miles from north to south) is so broken as to be 
known as the Uinkaret Mountains in contrast to the Uinkaret Plateau 
farther north.^ In sharp contrast to the rectilinear outlines and vivid 
colors of the greater part of the plateau region are the irregular profiles 
and gloomy aspect of the basaltic plateau of Mount Trumbull, a great 
mesa consisting of horizontal sedimentary strata capped by 500-600 
feet of basalt. Its summit (2000-3000 feet relative altitude) reaches 
to such a height that the climate is cool and moist and the plateau 
sustains a forest growth of yellow pine. About the mesa or mountain 
and covering the whole southern end of the Uinkaret Plateau are great 
lava flows — jagged masses of black basalt, desolate except for an occa- 
sional grove of cedar and piiion.^ 

From the summit of Mount Trumbull 120 to 130 cinder cones are 
visible and upon the whole Uinkaret are 160 to 170 vents in all. None 
of them in the main field is of great size; the highest are only 700 or 
800 feet in altitude, with a diameter of a mile. 

KANAB PLATEAU 

The Kanab Plateau is separated from the Uinkaret by an incon- 
spicuous boundary. For about 20 miles north of the canyon it is 
clearly marked by the line of cliffs along the Torowxap fault which grad- 
ually dies out northward, and beyond this point no prominent topo- 
graphic feature forms a dividing line.^ 

The Uinkaret and Kanab plateaus are separated from each other by 
the twenty-mile long Toroweap Valley, the locus of the Toroweap fault 
that causes the eastern wall of the valley to be several hundred feet 
higher than the western. The greatest displacement along the line of 
the fault is only 700 feet. It extends but 18 or 20 miles north of the 
canyon, hence is a much weaker boundary than the neighboring faults. 

' The heights of the various fault scarps should not be taken as an indication of the amount 
of faulting. While the Grand Wash Cliffs are from 2000 to 3000 feet high, the fault which 
gave rise to them exhibits 6000 feet maximum vertical displacement. Likewise Hurricane 
Ledge is from 500 to 2000 feet high, but it is associated with a maximum displacement of about 
12,000 feet 10 miles north of the Virgin River Valley. (Button, idem, p. 20.) 

2 See the Mount Trumbull quadrangle, U. S. Geol. Surv. 

3 C. E. Button, Tertiary History of the Grand Canyon Bistrict, Mon. U. S. Geol. Surv., 
vol. 2, 1882, pp. 81-84, 103- 

* Idem, p. 13. 



COLORADO PLATEAUS 27 1 

KAIBAB PLATEAU 

The Kaibab and Kanab plateaus are separated by the West Kaibab 
fault. The eastern border of the Kaibab Plateau is not formed mainly 
by faulting, hence it is an exception to the general rule. Here occurs 
not a fault but a great monoclinal flexure that is partially and locally 
faulted on a small scale and with a total descent of about 4000 feet. 
About mid-length it becomes a double monocline and finally a double 
fault before reaching the Colorado. The whole displacement dies out 
south of the Colorado. The Kaibab Plateau is thus a great uplifted 
block between two parallel lines of displacement, the eastern a com- 
pound flexure, the western a fault. The western border fault continues 
southward for but a short distance before splitting into three secondary 
faults with associated scarps and these extend almost to the brink of 
the Grand Canyon.^ 

The northern end of the Kaibab is a great cusp which terminates a 
little south of the town of Paria. Its southern border is the mile-deep 
Grand Canyon of the Colorado. Structurally and topographically the 
Kaibab is continued across the canyon into the southern district, but 
the strong break of the canyon has caused the adoption of a different 
name for the southern section, which is called the Coconino Plateau. 

It would be reducing to common terms that which is in the highest 
degree uncommon if no mention were here made of the extraordinary 
scenic features displayed in this greatest wonderland of North America. 
Even superlative terms are feeble, and ordinary language is wholly in- 
adequate for the expression of forms and colors that have been the 
theme of every enthusiastic scientist and every poet who has beheld 
the great cliffs, profound canyons, and vast expanses of the plateau 
region. Button's rich vocabulary enabled him to write a description 
which is probably the most satisfactory expression of the ideas and 
feelings which these great scenic features inspire. We therefore restrict 
ourselves to two or three quotations from his classic memoirs. Tertiary 
History of the Grand Canyon District and Geology of the High Plateaus of 
Utah. They are not the most enthusiastic passages that may be found; 
they are rather the most restrained and careful and ma,y therefore be 
accepted not only as scientific but also as imaginative and interesting. 
The first description presents the region of terraces and canyons east 
and south of the High Plateaus of Utah as seen from one of the latter 
at an altitude of more than 11,000 feet. 

1 C. E. Button, Tertiary History of the Grand Canyon District, Mon. U. S. Geol. Surv., 
vol. 2, 1882, p. 13. 



272 FOREST PHYSIOGRAPHY 

"... the eye ranges over a vast expanse of nearly level terraces, bounded by cliffs of 
strange aspect, which are truly marvelous, whether we consider their magnitude, their seem- 
ingly interminable length, their great number, or their singular sculpture. They wind about 
in all directions, here throwing out a great promontory, there receding in a deep bay, but con- 
tinuing on and on until they sink below the horizon, or swing behind some loftier mass, or 
fade out in the distant haze. Each cliff marks the boundary of a geographical terrace sloping 
gently backward from its crest line to the foot of the next terrace behind it, and each [in 
northward succession] marks a higher and higher horizon in the geological scale as we ap- 
proach its face. Very wonderful at times is the sculpture of these majestic walls. Panels, 
pilasters, niches, alcoves, and buttresses, needing not the sHghtest assistance from the im- 
agination to point the resemblance; grotesque forms, neatly carved out of solid rock, which 
pique the imagination to find analogies; endless repetitions of meaningless shapes fretting the 
entablatures are presented to us on every side, and fill us with wonder as we pass." 1 " Isolated 
masses cut off from the main formation, and often at considerable distances from it, lie with a 
majestic repose upon the broad expanse of the terrace. These sorhetimes become very striking 
in their forms. They remind us of great forts with bastions and scarps nearly a thousand 
feet high. The smaller masses become regular truncated cones with bare slopes. Some of 
them take the form of great domes where the eagles may build their nests in perfect safety. 
But noblest of all are the white summits of the great temples of the Virgin gleaming through 
the haze. Here Nature has changed her mood from levity to religious solemnity, and revealed 
her fervor in forms and structures more beautiful than anything in human art." - 

"But of all the characters of this unparalleled scenery that which appeals most strongly to 
the eye is the color. The gentle tints of an eastern landscape, the rich blue of distant moun- 
tains, the green of vernal and summer vegetation, the subdued colors of hillside and meadows 
all are wanting here, and in their place we behold belts of fierce staring red, yellow, and toned 
white, which are intensified rather than alleviated by alternating belts of dark iron gray." ' 
"As the sun nears the horizon the desert scenery becomes exquisitely beautiful. The deep 
rich hues of the Permian, the intense red of the VermiHon Cliffs, the lustrous white of the dis- 
tant Jurassic headlands are greatly heightened in tone and seem self-luminous. But more than 
all, the flood of purple and blue which is in the very air, bathing not only the naked rock faces 
but even the obscurely tinted fronts of the Kaibab and the pale brown of the desert surface, 
clothes the landscape with its greatest charm. It is seen in its climax only in the dying hours of 
daylight." ^ 

SAN FRANCISCO PLATEAU 

The term is here employed to include the whole region between the 
Grand Wash Cliffs, the Arizona Highlands, the Grand Canyon Dis- 
trict, and the Little Colorado River. It includes the Coconino Pla- 
teau on the north, and on the south the broad platform of much greater 
extent upon which the San Francisco Mountains stand. ^ Its general 

I Geology of the High Plateaus of Utah, p. 8. 

- Description of the scenery of the White Cliffs, developed upon the white Jurassic sand- 
stone. From Tertiary History of the Grand Canyon District, p. 37. 

3 From description of the same region noted in the first quotation from Geology of the 
High Plateaus of Utah, p. 8. 

^ Impressions of a sunset on the Kanab Plateau in Tertiary History of the Grand Canyon 
District, pp. 124-125. 

5 It is somewhat confusing to use the term Colorado Plateau for this portion of the district 
as in Dutton's standard description. The term Colorado had already been established for the 
entire province. Both the Land Office maps and the maps of the Topographic Branch of the 
U. S. Geological Survey follow Dutton's usage however. In using the term San Francisco 
Plateau I am following the excellent suggestion of Robinson (Am. Jour. Sci., vol. 24, 1907). 



COLORADO PLATEAUS 



altitude is from 7000 to 7500 feet, which 
is distinctly higher than the plateaus im- 
mediately north of the canyon, except the 
Kaibab. The strata of the district are 
nearly horizontal though with a broad re- 
gional slope toward the southwest, and, 
with few exceptions, the surface is not 
deeply or extensively scored by canyons. 
Unlike the Kaibab it has no strongly 
marked divisional boundaries, since the 
great fault scarps which form such promi- 
nent features of the one are either absent 
or diminish in height or disappear in the 
other. Its surface is diversified in some 
localities by (i) low, lava-capped, and usu- 
ally forest-clad mesas, as Black Mesa and 
Mogollon Mesa, and (2) volcanic cones and 
peaks such as San Francisco Mountains 
(13,000) and the associated lava flows about 
their bases. ^ Some of the volcanoes are 
very recent, as in the San Francisco Moun- 
tain region, an example 16 miles north of 
San Francisco Mountain being probably 
not more than 100 or 200 years old.^ 



273 



M^^i] 



Southern Plateau District 



zuNi plateau 

The Zuiii Plateau (locally called the Zuni 
Mountains) is an illustration of a type of 
structure seen in a number of places in the 
plateau country, for example in the San 
Rafael Swell on the eastern margin of 
the High Plateaus, and is of special physi- 
ographic interest. The otherwise flat pla- 
teau strata have been somewhat locally 

1 C. E. Button, Tertiary History of the Grand Canyon 
District, Mon. U. S. Geol. Surv., vol. i, 1S82, pp. 14-15. 

2 D. W. Johnson, A Recent Volcano in the San Fran- 
cisco Mountain Region, Arizona, Bull. Geog. Soc. Phil., 
vol. 5, igo7, pp. 2-6. 



274 



FOREST PHYSIOGRAPHY 



uplifted, raising the surface well above the general level and 
exposing it to pronounced erosion. The cross section, Fig. 77, 
exhibits the main structural features. It will be readily seen 
that the margins of the uplifted tract have been structurally 
bent and in places faulted, but that the summit of the uplift is 
almost flat. The erosion of the superior part of the broad 
uplift has removed portions of the capping layers and exposed 
the geologic section ranging from rather young (Cretaceous) 
to very old rocks (Archaean). Each stratum ends in a cliff 
facing the central axis of the uplift, and each cliff may be traced 
in the form of a great oval entirely around the tract. Each 
stratum also dips outward from the cliff summit and extends 
below the next cliff of the younger formation overlying it. The 
heart of the uplift is composed of Archaean gneisses and mica 
schists, and these constitute the main summit platform or 
plateau over a considerable portion. Since the summit has 
this constitution the oldest (stratigraphically the lowest but 
topographically the. highest) sedimentary formation, the Car- 
boniferous, ends at the shoulder or margin of the main platform. 
Many portions of the summit have strongly marked topo- 
graphic features and are very rugged and diversified, being 
deeply scored with canyons. The principal drainage lines cross 
portions of the uplift regardless of the structure and show that 
they were determined before the uplift, a feature of common 
occurrence throughout the plateau country, while it is equally 
common to find all the lesser stream-ways in close sympathy 
with the broad structural surfaces of the main plateaus.^ 

MOKI-NAVAJO COUNTRY ^ 

That part of Arizona bounded by the San Juan, the Colorado, 
Little Colorado, and Puerco rivers reveals in slightly modified 
form the typical characteristics of the plateau province. The 
river valleys are canyons or wide, open washes, the rocks are 
chiefly sedimentaries of Mesozoic age, the climate is arid, the 
vegetation sparse, and there is little prospect that the area can 
be made profitable to civilized man. The only permanent 
streams are the San Juan, the Colorado, and the headwaters of 






• C. E. Button, Mount Taylor and the Zufii Plateau, 6th Ann. Rept. U. S. 
Geol. Surv., 1884-1885, pp. 162-163. 

2 In the absence of published data on this section of the plateau country Prof. 
H. E. Gregory has kindly prepared this brief description from his field notes. 



COLORADO PLATEAUS 275 

a few rivers which come from the highlands; for example, Chinlee, 
Moencopie, Navajo, and Little Colorado, Plate II. 

During the rainy season (July and August) the run-off from the high- 
lands is so rapid and uncontrolled and the flat valley washes are so 
thoroughly drowned that travel is exceedingly difficult and often danger- 
ous; and the utilization of the extensive alluvial bottoms for agriculture 
on a large scale is rendered impossible. None of the important streams 
is reduced to grade throughout its course. All of them are carrying 
prodigious quantities of waste to be added to the burden of the Colo- 
rado. In the absence of running streams the Navajos and Hopis depend 
for themselves and their stock upon springs and ephemeral lakes, and 
the supply at best is meager and commonly unpalatable. It is re- 
markable how little water is used by man and beast. 

The broad structural features of the region are easily comprehended. 
The highlands along the Arizona-New Mexico line include Carrisos 
Mountains at the north, the Lukachukai, Tunichai, and Choiskai moun- 
tains, and the hogback ridges between Fort Defiance and Gallup. The 
Carrisos (elevation 9420 feet) rise 5000 feet above the San Juan at their 
base, and constitute one of the most prominent landmarks of the pla- 
teau country. The mountains are laccolithic in origin and are caused 
by irregular intrusions of quartz-monzonite which deformed Triassic, 
Jurassic, and Cretaceous sandstone into a group of domes. Subse- 
quent erosion has removed the cover here and there, exposing the igne- 
ous core, and deeply trenched the heavy sedimentary beds which form 
the flanks of the uplift. Lukachukai, Tunichai, and Choiskai moun- 
tains are composed of sedimentary strata lying approximately hori- 
zontal; their elevation is due to a fold of great amplitude, the western 
limb of which forms the eastern side of the Chinlee Valley. Caps of 
lava rest upon the Tunichais as well as upon a number of detached 
buttes at the south, while the covering beds of the Choiskais are Ter- 
tiary sediments. The ridges south and east of Fort Defiance are formed 
by the resistant members of Mesozoic strata which here dip to the east 
at a high angle. 

The area between the lower Chinlee and Colorado rivers is part of 
a great dome of Triassic and Jurassic sediments intersected by the 
San Juan River. At Marsh Pass the strata plunge beneath the Creta- 
ceous of the great Zilh-le-jini (Navajo for Black Mountain) mesa, and 
the hogback rim of the dome is prominently exposed from Marsh Pass, 
Arizona, to Elk Ridge, Utah. The elevation at Skeleton Mesa and the 
region about the head of Pahute Canyon is attained by a series of mono- 
clinal folds with steep eastern limbs. As one travels from the Chinlee 



276 FOREST PHYSIOGRAPHY 

westward he ascends a series of giant steps until an elevation of nearly 
8000 feet is reached. Standing on the plateau at this elevation his 
view is unobstructed except for Navajo Mountain (10,400 feet), a lacco- 
lith with its sedimentary cover still intact. It stands as' an island 
covered with vegetation in the midst of a sea of barren red rock. From 
the top of Navajo Mountain a more comprehensive view of the plateau 
province may be obtained than from any other point. From Lee's 
Ferry the Leupp Echo Cliffs and their southern continuation mark the 
line to which the Jurassic and Upper Triassic have been stripped by the 
tributaries of the Colorado and the Little Colorado. 

In the center of the Navajo Reservation and including most of the 
Hopi Reservation is the Zilh-le-jini mesa, attaining an elevation of 6000 
to 8000 feet, and bordered on all sides by steep escarpments. In struc- 
ture this highland is a shallow syncline of Cretaceous strata in which 
are included valuable beds of coal. On the narrow finger-like mesas 
forming the southern border of Zilh-le-jini are located the six villages 
of the Hopis which constitute the ancient province of Tusayan. Be- 
tween Tusayan and the Little Colorado is an extensive area of lava- 
capped mesas and volcanic necks and dikes, the remnants of early 
Tertiary lava flows. 

The vegetation is characteristic of the plateau province. Above 
7000 feet on the highlands along the Arizona-New Mexico boundary 
line there grows an open stand of yellow pine which is used for the manu- 
facture of rough lumber for various government projects. Pine in lim- 
ited amounts grows on the northern rim of Zilh-le-jini mesa and covers 
the upper slopes of Navajo Mountain. Between 6000 and 7000 feet, 
pinon and cedar are commonly found, but over wide areas it averages 
not more than two or three trees per acre. Sage-brush and greasewood 
grow in limited amounts at elevations below 6000 feet, and grass, which 
is fairly abundant at higher elevations, is also found in limited amounts 
below 6000 feet, and in a few favorable localities forms a continuous sod. 
The extent of bare rock and sand floor is very great, and probably not 
more than 10% of the Navajo-Moki region is actually covered with 
vegetation. In fact it is possible to walk from Gallup, New Mexico, 
to Tanner's Crossing on the Little Colorado, or from the Carrisos Moun- 
tains to Lee's Ferry, without stepping on a twig or a spear of grass. 

» 

Grand River District 

West of -the Rocky Mountains of central Colorado, Plate II, and 
on meridian 107° 30' is the northeastern edge of the Colorado Plateaus. 
This portion is called the Grand River district after the main drainage 



COLORADO PLATEAUS 277 

line. It consists of the White River Plateau, Grand Mesa, the Book or 
Roan Plateau, the Uncompahgre Plateau, and the Dolores Plateau, named 
in order from north to south. The strata upon which these plateaus are 
developed as a rule dip toward the west and away from the Rocky 
Mountains. In the southwestern part of Colorado, along the San Juan 
Valley, six well-marked groups of hard rock (sandstone) occur and a 
corresponding number of soft shales alternate with them and form lines 
of weakness for the attack of the weather. Each group of strata slopes 
and dips gently westward until a break occurs and a precipitous descent 
is made across the edges of the rock layers to the next lower group of 
strata,^ a succession that is typical of the district, although the number 
of alternations of strata and to some extent the topographic expression 
varies from section to section. 

Like the other districts the Grand River district exhibits a number of 
mountain groups of igneous origin scattered upon its plateau surfaces. 
These include the San Miguel, La Plata, Carriso, Abajo, and other 
groups, which are as a rule of laccolithic origin. Erosion has removed 
the once overlying sedimentary beds and exposed the intruded rock. 

WHITE RIVER PLATEAU 

The White River Plateau is the northernmost of the series in the north- 
eastern part of the plateau province. The general level of its surface 
is interrupted in many places by higher summits (500-1000 feet above 
the general level) and ranges of mountains on the one hand and by 
deep valleys and canyons on the other. While plateau surfaces are 
still conspicuous features of the region, the upland has been so largely 
cut away by erosion, so largely modified by uplift or faulting of the once 
flat-lying strata, so complicated by intruded masses of igneous rocks, 
that the plateau feature can scarcely be said to be the dominating one, 
and by some the plateau would be classified as a part of the Rocky 
Mountains. The best-preserved sections of the plateau are those whose 
flat upper surfaces have been unbroken and but slightly tilted. 

The White River Plateau has been formed largely by lava flows, 
the borders of which have been cut into deep gorges and ravines in 
which some of the headwaters of the White and Yampa rivers take 
their rise.- On the west especially this plateau falls off in abrupt and 
high cliffs to the long slopes of the bordering spurs; the eastern border 
is marked by high detached masses which give it a mountainous aspect 

1 C. E. Button, Mount Taylor and the Zuni Plateau, 6th Ann. Rept. U. S. Geol. Surv., 
1884-1885, p. 242. 

2 F. V. Hayden, U. S. Geog. and Geol. Surv. of the Terr., 1876, p. 7. 



278 FOREST PHYSIOGRAPHY 

when viewed from the east. North of the White River Plateau the 
country is mountainous and so broken that no distinct, well-defined 
topographic system has been determined.^ On the south the plateau 
forms the divide between the White and the Grand rivers a^id loses its 
distinctive mesa-like quality, being cut by profound canyons.^ 

SPECIAL BORDER FEATURES 

In portions of northwestern Colorado the plateau character is largely 
replaced by hogback or monoclinal ridges, strike valleys, and other fea- 
tures related to moderate complexities of structure developed in a series 
of alternating hard and soft strata.''* 

One of the most remarkable physiographic features of northwestern 
Colorado is Grand Hogback, which extends southward from the Dan- 
forth Hills to a point beyond Grand River. Indeed under the name of 
Colorado Ridge it continues far beyond Grand River to the point where 
its identity is lost in the more rugged West Elk Range. The Grand 
Hogback is bordered on both sides by long continuous valleys; the 
ridge itself is at some places a single-, at others a double-crested hog- 
back ridge formed by the outcrop of massive sandstone ridges inclined 
eastward at steep angles. Its steep inclination has afforded opportunity 
for the development of an exceedingly rugged topography whose principal 
elements are precipitous marginal slopes. The most striking features 
of the Grand Hogback and the Colorado Ridge are their topographic 
continuity and structural uniformity. The stream valleys in the Hog- 
back Ridge contain a small amount of red fir, while the upper slopes 
and crest, 2000 feet above the marginal valley bottoms, are covered with 
a dense growth of oak brush, chokecherry, and juniper.* 

ROAN OR BOOK PLATEAU 

One of the most striking topographic features of the Grand River dis- 
trict is the southern margin of the Roan or Book Plateau, the Roan or 
Book Cliffs.^ In places the cliffs rise almost vertically from the edge of 
the Grand River Valley to their full height ; elsewhere the ascent is by a 
succession of broken steps. Their mean height is about 8600 feet, or 

1 S. B. Ladd, U. S. Geog. and Geol. Surv. of Colorado and Adj. Terr. (Hayden Surveys), 
1874. PP- 437-438- 

2 Idem, p. 4SQ. 

s H. S. Gale, Gold Fields of Northwestern Colorado and Northeastern Utah, Bull. U. S. 
Geol. Surv No. 415, 1910, p. 24. 

' Idem, p. 31. 

6 Roan, from their prevailing color; Book, from the resemblance of their characteristic form 
to a bound book. 



COLORADO PLATEAUS 279 

3500 feet above the Grand River. They are the southern escarpment of 
the plateau of the same name which slopes rather gently to the north 
and northeast and is drained by tributaries of the White River. Nearly 
half the original surface of the plateau is still intact, so that a rather 
flat aspect is more common than in the more dissected White River 
Plateau on the east or the Uncompahgre Plateau on the south. The 
western is the most dissected portion of the plateau, and here the divide 
is in places only 30 or 40 feet wide, bordered on the chff side (south) by 
a precipice and on the plateau side by a strong slope. The crest of the 
cliffs has very little water on account of the low elevation (8600 feet) ; it 
is covered in the main with grass and sage. Almost the only arboreal 
vegetation is quaking aspen, which occurs but sparingly; there are but 
a few occurrences of spruce and pine.'^ 

UNCOMPAHGRE PLATEAU 

The Uncompahgre Plateau lies between the Uncompahgre Mountains 
and the Grand River. It is 90 miles long and from 15 to 25 miles wide; 
its elevation is from 8600 to 10,200 feet (northwest). It is in the form 
of a broad arch of sedimentary beds about 1000 feet thick over a cen- 
tral core of granite, the latter being well exposed in the steep and beauti- 
ful canyon of the Unaweep, where it forms two-thirds of the height of 
the walls. The tributaries of the Unaweep have all cut down to the 
granite, and in the season of floods due to the melting of the snows their 
waters drop from 300 to 2000 feet to the bed of the main canyon 
below. On the west the plateau is bordered by steep cliffs which 
descend to the valleys or canyons of the Grand and other streams. 

One of the most profound canyons of the whole mountainous western 
half of Colorado is that of the Gunnison on the northeastern border of 
the Uncompahgre Plateau. It is 56 miles long and 3000 feet deep in 
the deepest part. The plateau in which it is incised consists of granite- 
gneiss capped by 1000 to 1200 feet of sedimentary strata. The canyon 
is cut through the overlying sedimentary rock and deep into the gneiss, 
the contact being marked by a sloping bench below which are rough, 
ragged, and nearly vertical walls which extend to the river margin; above 
the contact are steeply sloping talus and vertical cliff in alternating 
series. The tributaries of the Gunnison have incised their courses but 
little into the gneiss and therefore have very steep descents where they 
join the master stream.^ 

1 F. V. Hayden, U. S. Geog. and Geol. Surv. of the Terr., 1875, p. 346, and 1876, p. 69. 

2 Henry Gannett, U. S. Geol. and Geog. Surv. of Col. and Adj. Terr. (Hayden Surveys), 
1874, P- 425- 



28o FOREST PHYSIOGRAPHY 

The influence of elevation upon rainfall and thus upon the character 
and amount of the vegetation is admirably illustrated in the Un- 
compahgre Plateau. In the interior of the plateau and down to an 
elevation of 7000 feet or more are streams and springs in some number, 
good pasturage, a sprinkling of aspen groves, and game in some quantity; 
below 7000 feet aspen gives way to pinon, grass to sage, cacti, and 
bare rock, the streams become muddy torrents or dry up altogether, 
and in place of the rolling plateau surface are deep narrow canyons and 
steep precipices.^ 

The influence of elevation upon the character of the vegetation is also 
well shown on the plateau between the Gunnison and the North Fork 
of the Gunnison. This plateau has a smooth unbroken summit sloping 
in a direction slightly west of north. It ranges in elevation from 9000 
to 5400 feet, and owing in part to its marked slope, which drains the 
surface water rapidly away, and in greater part to its low elevation, the 
plateau is without timber in contrast to the bordering mountains of 
slightly greater elevation. Its vegetation is pinon pine, cactus, sage- 
brush, and scrub oak in contrast to the timbered plateau on the east.^ 

DOLORES PLATEAU 

The Dolores Plateau lies between the Dolores and San Miguel rivers 
about halfway between the San Juan and Grand River canyons. The 
highest portion is known as Lone Mesa and is at 10,000 feet eleva- 
tion, with an area of about 40 square miles. About it are a number of 
high flat-topped buttes which like it are erosion remnants with steep 
bordering scarps. The superior elevation of Lone Mesa gives it a 
greater rainfall than falls on adjacent tracts and meadows, and forests 
of pine abound.^ 

The canyon of the Dolores is very narrow and precipitous, with almost 
no alluvial bottoms except in its shallowest portion at the great bend, 
Fig. 78. Here are a rich growth of grass, some Cottonwood groves and 
bushes, and vines. On the borders of the canyon below this point is a 
rather heavy growth of pinon pine and cedar, and on the various head- 
water branches are forest and meadow, aspen groves, and rich grassy 
parks in contrast to the desert canyon below.'* 

One of the most remarkable cases of stream direction not in accord 
with the present slope of the plateau surface (p. 284) is that of the 

1 F. V. Hayden, U. S. Geog. and Geol. Surv. of the Terr., 1875, pp. 340, 341, 349. 

2 Henry Gannett, U. S. Geol. and Geog. Surv. of Col. and Adj. Terr. (Hayden Surveys), 
1874, p. 426. 

3 Idem, p. 266. 

* Idem, pp. 266-277. 



COLORADO PLATEAUS 



2S1 



Dolores River, a tributary of the Grand. The Dolores rises in the San 
Juan Mountains, runs south and west for more than 30 miles, then flows 
northwest against the inclination of the surface for about 60 miles to the 
Grand River in western Colorado, in a gradually deepening canyon, 
Fig. 78. At the turning point it is in a canyon only 100 feet deep; 
above and below this point the canyon deepens to 2000 feet. Evidently 
the river gained its course sometime before the present surface con- 
ditions were established. The surface is structural in origin, being 
developed on a great sandstone layer (Dakota). Either the surface was 
peneplaned and the river now pursues an antecedent course with re- 




Fig. 78. ■ 



■ Canyon of the Dolores. The canyon is 2000 feet deep at a, 2100 at h, and 100 at c. 
(Hayden Surveys.) 



spect to later uplifts that deformed the peneplain, or its course was 
developed in response to a structural slope that has since been reversed. 
While the main stream has thus maintained its earlier course the 
smaller streams of the region show marked responses to the present 
attitude of the surface. The tributaries of the San Juan (south) rise 
almost on the brink of the Dolores canyon, for they have been extended 
in response to the structural surface now existing and have encroached 
on the weaker Dolores tributaries until the latter are all but extinguished 
south of the canyon.^ 

The Yellow Jacket tributary of the San Juan has encroached so far upon the Dolores at the 
great bend that a tunnel several hundred yards long has been constructed through the in- 
tervening barrier and a large part of the water of the Dolores turned into the Yellow Jacket 
for the purpose of irrigating the valley flats at Cortez, Plate IL 

Physiographic Development; Erosion Cycles 

An understanding of the physiography of the Colorado Plateaus re- 
quires at least some knowledge of its recent history as expressed in a 
number of topographic cycles through which the region has passed. 
With the long periods of deposition in the plateau region when it stood 



1 F. V. Hayden, 9th Ann. Kept. U. S. 
1877, pp. 263-264, and Plate 42, p. 264. 



Geog. and Geol. Surv. of the Territories, 1875, pub. 



282 FOREST PHYSIOGRAPHY 

at or below sea level we have little to do; nor is it necessary for an un- 
derstanding of existing topography to take account of the ancient and 
now buried surfaces of erosion that are so well exposed in the walls of 
the Grand Canyon. It is sufficient for our purpose to begin with 
rather late movements in the evenly bedded mass of strata accumulated 
by long-continued erosion of the Great Basin and adjacent mountains. 

In the Tertiary (latter part of the Eocene or possiblj' in early Miocene) the plateau region 
was uplifted and the uplift was accompanied by monoclinal folding. The result of these first 
deformations was an elevation of the western plateau country above the eastern, and the 
descent from plateau to plateau was at that time from west to east and not as at present from 
east to west. The folding probably gave rise to a number of qlosed basins in which lakes 
were formed and sediments laid down, although the drainage of the region was probably on the 
whole through basins draining to the sea. Since this first deformation of the plateau country 
(in Tertiary time) the region has suffered continuous erosion down to the present, although 
the character of the erosion, the geologic structure, and the topography, have been modified 
repeatedly, as outlined in the following paragraphs. 

In response to internal forces of the earth a period of faulting followed the first period of 
monoclinal folding and by it the plateau district was marked out and the eastern and western 
borders clearly defined through the lowering of the country on either side. The date of this 
period of faulting has not been closely ascertained, but it may be regarded with a certain 
degree of accuracy as having occurred at the close of the Miocene. 

FIRST EROSION CYCLE 

The two geologic events of monoclinal folding and of faulting lent 
to the relief of the plateau region a pronounced character. But the 
topographic expression of these structural features was gradually and 



Fig. 79. — Black Point Monocline, Colorado Plateaus, showing remnant of base-leveled surface 
capped by lava. i. Kaibab; 2. Moencopie; 3. Shinarump; 4. Basalt. (Robinson). 

at last completely obliterated at the close of a cycle of erosion known 
as "The Period of the Great Denudation." The surface of the entire 
southern plateau country, and probably also of the northern plateau 
country, was reduced to a peneplain. At the close of the great denuda- 
tion cycle there occurred widespread eruptions of basalt. The lava flows 
capped portions of the surface of the peneplain and thus protected 
them from the effects of later denudation. 

An instructive locality for the study of those features upon which the foregoing description 
rests is at Black Point in the Little Colorado Valley, where the Black Point monocline dips 
eastward as shown in the cross section, Fig. yg. The black basalt which caps the surface of 
the country and preserves a portion of the ancient peneplain rests upon an exceedingly smooth, 
almost flat surface, a degree of smoothness that could not have been developed across strata 



COLORADO PLATEAUS 283 

of such variable hardness except at a base level of erosion. The Kaibab cherty limestone is 
very resistant, v/hile the Moencopie soft sandstone and shales and the Shinarump marls are 
very soft and easily weathered; above the marls at the eastern end of the section is a compact 
sandstone of most resistant quality. A similar occurrence is at Anderson Mesa, eight miles 
southeast of Flagstaff, where a smooth surface was once developed across rocks of very differ- 
ent hardness such as the Kaibab cherty limestone and the soft Moencopie shales. The 
peneplain is also well shown in the Mount Taylor region on the walls of both the Mount 
Taylor and the Prieta mesas where it bevels across beds of slight dip. Its character as in- 
ferred from the once buried remnants now reexposed was that of a surface of rather faint 
relief. 1 Huntington and Goldthwaite^ have described it in the Toquerville district, Utah, and 
Davis has interpreted phenomena of the same significance in a number of other localities. 

The boundaries of the known portions 'of the base-leveled surface in- 
clude about 25,000 square miles of country, and it seems at present as if 
these peneplain remnants in various portions of the plateau country 
were at one time united so as to form a surface of very slight relief, 
out of which the existing plateaus were blocked by faults. Recently 
the work of Gregory^ in the Navajo country and the valley of the San 
Juan has shown the extension of the great peneplain surface far to the 
north. An excellent locality is between Tuba City and Oraibi, where a 
remarkably fiat surface only partially dissected bevels regularly across 
strata of pronounced dip and structural variation. The entire extent 
of the peneplain will only be known when the now little explored 
portions of the province (which aggregate the greater part of it) are 
examined and the physiography interpreted. 

SECOND EROSION CYCLE 

The next important geologic event in the plateau region was the 
inauguration of a second period of faulting near the close of the Pliocene, 
a period of faulting in which the plateau region was again strongly 
blocked out and given those features that are most prominent at the 
present time. The second period of faulting increased the relief of the 
plateau region and resulted in the pronounced step-like relation of 
the different members of the plateau. While the folding of the first 
period of deformation operated in such a manner as to cause a descend- 
ing series of plateaus from west to east, the major faults of later dates 
reversed the order of descent, an order that has been maintained down 
to the present. 

The second period of faulting introduced the second or post-peneplain 
cycle of erosion, in which there was developed a widespread system of 

1 D. W. Johnson, Volcanic Necks of the Mount Taylor Region, New Mexico Bull. Geol, 
Soc. Am., vol. 18, 1907, pp. 307-308. See also idem, cross section, Fig. 2, p. 309. 

2 Huntington and Goldthwait, The Hurricane Fault in the Toquerville District, Utah, 
Bull. Mus. Comp. Zool., vol. 42, Geol. Series, vol. 6, 1903. 

3 Personal communication. 



284 FOREST PHYSIOGRAPHY 

shallow but mature valleys, one of the most persistent features of the 
better-known portions of the province. The drainage characteristics of 
this partial cycle have been noted by several writers, among whom 
Robinson was the first to demonstrate their persistence ^nd their 
meaning in terms of erosion cycles.^ The same feature has been de- 
scribed by Noble,^ who says: 

"The drainage system of the plateau surface (Coconino) consists of a series, of mature open- 
floored valleys with gentlj' sloping sides, which contain no living streams. ... In tracing one 
of these mature valleys toward its head . . . [it is] common . . . to find it truncated as a hanging 
valley by the wall of the Grand Canyon. . . . The same system of mature valleys covers 
[the] surface [of the Kaibab plateau] which slopes southwesterly to, the rim of the canyon." 

The surface drainage of the Kaibab now runs through this system of 
mature valleys into the Grand Canyon; the surface drainage of the 
Coconino runs through a similar valley system away from the Grand 
Canyon, and both plateaus have only temporary streams. These mature 
drainage systems offer the most striking contrast on the one hand to 
the youthful topography of the deeply trenched canyon developed 
in the third or next erosion cycle, and on the other hand to the base- 
leveled surface now preserved in fragments beneath the basalt caps of 
various mesas. 

It should not be thought that the second cycle of erosion brought 
about any great vertical reduction of the surface. On the contrary 
the depth to which the streams cut in response to the new base level was 
only a few hundred feet as against the few thousand feet of the third 
and last, or canyon cycle of erosion. The chief result of denudation 
in the second cycle was the broad horizontal stripping back of the 
strata outcropping on the surfaces of the plateaus and the development 
of mature valley systems. The stripping of the gently inclined strata 
proceeded on structural planes, so that the present flat plateau surfaces 
are structural surfaces developed upon the upper surface of resistant 
strata. Generally the structure dips uniformly toward the southwest 
at the rate of about 200 feet to the mile, so that the surfaces of the 
Coconino and San Francisco plateaus south of the Grand Canyon 
slope to the southwest from the canyon rim at the rate of about 200 
feet per mile. The Kaibab plateau north of the Colorado Canyon slopes 
southwesterly in the same degree to the rim of the canyon. It is for 
this reason that the southern plateau drains away from the canyon and 
that the northern plateau drains into it. The plateau surfaces are 

1 H. H. Robinson, A New Erosion Cycle in the Grand Canyon District, Arizona, Jour. 
Geol., vol. 18, 1910, pp. 742-763. 

2 L. F. Noble, Contributions to the Geology of the Grand Canyon, Arizona, The Geology 
of the Shinumo Area, Am. Jour. Sci., vol. 29, 1910, pp. 374-380. 



COLORADO PLATEAUS 285 

everywhere accordant with the rock structure.^ These facts must be 
thoroughly appreciated because, while the plateau as a whole has been 
base-leveled, the remnants of the ancient base-leveled surface total a very 
small area, and in general are preserved only beneath lava caps near 
the summits of mesas. 

THIRD EROSION CYCLE 

The third period of faulting and of regional uplift inaugurated a 
third cycle of erosion, and, because the most striking effects of erosion in 
this cycle are the great canyons of the region, it has been called the 
"Canyon Cycle of Erosion." During this cycle a certain amount of 
plateau stripping has taken place and the cliff profiles have been re- 
freshed, although the chief result has been the development of the 
profound canyons of the great Colorado and its principal tributaries. 

During the canyon cycle of erosion there occurred a third period of volcanic activity char- 
acterized by eruptions of basalt from many small volcanic cones. The later eruptions took 
place, as a rule, before or during the period of glaciation, since they have been glacially 
modified, although a few cones and iiows are of very recent geologic age. The later basaltic 
flows may be distinguished from the earlier flows capping the surface of the peneplain by their 
freshness, their undissected condition, and the absence of those displacements which afi'ected 
the earlier volcanic flows.2 

With these historical events in mind we may now turn to some fea- 
tures of the existing topography of the Colorado Canyon that require 



Ml 



Fig. 80. — Cross-proiile of the Grand Canyon of the Colorado River. Scale, one inch = 15,000 feet. 
I, inner gorge; 2, 5, 7, sandstone; 4, 8, limestone; 3, 6, shale. (Gilbert and Brigham.) 

more detailed study. The main section of the canyon is known as the 
Grand Canyon. Above the Grand Canyon is the Marble Canyon 
(cut into Carboniferous limestone) a feature of great magnitude but 
dwarfed by the adjacent highly diversified Kaibab division of the Grand 
Canyon, more than a mile deep (6000 feet). The length of the Marble 
Canyon is 65 miles, that of the Grand Canyon about 125 miles. 

The two main divisions of the Grand Canyon are the Kaibab and the 
Kanab, which have certain topographic contrasts of importance. In 

1 L. F. Noble, Contributions to the Geology of the Grand Canyon, Arizona, The Geology 
of the Shinumo Area, Am. Jour. Sci., vol. 29, 1910, pp. 374-380. 

- H. H. Robinson, Tertiary Peneplain of the Plateau District and Adjacent Country in Arizona, 
and New Mexico, Am. Jour. Sci., vol. 24, igo;, pp. 110-112. 



286 



FOREST PHYSIOGRAPHY 



the Kaibab division of the canyon the descent of the wall is unusually 
abrupt over the entire series of sedimentary rock. The only well- 
defined terrace is that developed upon the summit of the basal sand- 
stone of the Tonto group near the bottom of the canyon ^ a terrace 
known as the Tonto platform. Below the platform is an inner gorge 
formed upon the basement schists (Algonkian). The platform aver- 
ages a mile wide on either side of the canyon and is well enough 
defined to make travel upon it possible. In the Kanab division to the 
west the lower terrace has disappeared and a different terrace has been 
developed upon the summit of the Red Wall limestone about a thousand 
feet below the level of the canyon rim. Through it as through the 
Tonto platform is cut a deep narrow inner gorge. This platform or 
terrace is known as the Esplanade; it averages two miles in width on 
either side of the canyon. 

Still further differences may be seen in the aspect of these two sections of the canyon. The 
topography of the Kaibab division exhibits much greater dissection than that of the Kanab. 
The former is diversified by great amphitheaters thronged with buttes and outliers and 
trenched by a multitude of tributary gorges. In the Kanab division a very simple topography 
is found. There is a fairly regular broad outer canyon in which is cut an inner gorge, and the 
fantastic scenery of the Kaibab division is here wholly absent.! 

Climatic Features and Vegetation 

The distribution of temperature and rainfall according to relief or 
elevation is brought out strikingly in the plateau province. An inch 



Lower Colorado 
Basin 



San Francisco 

Mts, 



Colorado Plateaus 




2,7 in. Sea Level 

Fig. Si. — Topographic profile in relation to rainfall distribution from southwest to northeast across the 
three physiographic provinces of Arizona. 

of rainfall is the normal increase for every 500 feet of altitude on the 
border of the plateaus; about half this increase in altitude is required 
for an increase of an inch of rainfall within the border of the plateaus. 
Yet most of the plateaus are dry, almost as dry as the plains of south- 
western Arizona at half the altitude above sea level. The dryness is 
explained chiefly by the effect of the abrupt southwestern and western 
border in draining the passing winds of water vapor. 

1 L. F. Noble, loc. cit., p. 375. 



COLORADO PLATEAUS 287 

Below an altitude of 7000 feet the rainfall of the Colorado Plateaus 
is probably not more than 8 inches a year. With increase of altitude 
above that figure there is increasing rainfall and the highest of the 
High Plateaus receive the equivalent of about 24 inches of rain, though 
a large part of it occurs in the winter months and is mostly in the form 
of snow.i They are favored however with a summer maximum in 
July and August. Indeed Dutton estimates their summit rainfall at 30 
inches.^ The High Plateaus are therefore not arid; they are the first 
prominent topographic barrier which the winds strike east of the Sierra 
Nevada. 

The natural vegetation of the Rio Grande Valley on the southeastern 
border of the plateau country is limited to scanty grass, cottonwoods, 
and willows on the river bottoms, and to cacti and other desert forms 
on the higher slopes. At still greater elevations the junipers begin to 
come in, at first as gnarled stunted growths, then in better form, and on 
the slopes of the volcanic mountains, as Mount Taylor and the San 
Francisco Mountains, and on the summits and to some extent on the 
slopes of the higher mesas such as Mogollon Mesa, Black Mesa, and the 
Zuhi Plateau are thousands of square miles of magnificent forests of 
yellow pine and spruce.^ 

This is the usual succession of vegetation in the plateau country. 
The altitudinal range of timber species is sometimes not clearly defined 
on account of diversity of climatic conditions and exposure. At the 
headwaters of the East Clearwater, a tributary of the Little Colorado, 
the shady northward facing canyon slopes and walls are timbered with 
red fir and white fir, while the drier southward facing slopes are covered 
entirely with yellow pine.^ The most valuable tree of the region is the 
yellow pine; the sugar pine is found only on the southern plateaus and 
is rarely of commercial size; the pihon pine and the pitch pine are 
common but not valuable growths and usually occur on talus slopes. 
Engelmann spruce occupies the highest elevations and is the only 
timber above 11,000 feet, attaining its best growth at 10,000 feet and 
disappearing at 11,500 feet. The great height at which it grows makes 
it difficult to secure; and to the altitude is added the difficulty of the 

1 A. H. Thompson, in Powell's Lands of the Arid Region, U. S. Geog. and Gaol. Surv. of the 
Rocky Mountain Region, 1879, p. 151. 

2 C. E. Dutton, Geology of the High Plateaus of Utah, U. S. Geog. and Geol. Surv., 1889, 
p. 41. 

3 C. E. Dutton, Mount Taylor and the Zuiii Plateau, 6th Ann. Rept. U. S. Geol. Surv., 1884- 
1885, p. 125. 

1 F. G. Plummer, Forest Conditions in the Black Mesa Forest Reserve, Arizona, Prof. Paper 
U.S. Geol. Surv. No. 23, 1904, p. 16. . 



288 FOREST PHYSIOGRAPHY 

broken canyoned country between its plateau and mountain home and 
the valleys where the people live.^ 

The growth of grass is in most places scant, and at lower elevations 
diminishes in quantity and disappears in the lower and more desert 
country except where springs occur. The grasses grow characteristically 
in bunches and are thus in part protected among themselves from wind 
and blown sand- They have large strong stems and are not easily broken 
down by the infrequent rains and snows. They cure on the stalk and 
are highly nutritious, furnishing winter pasturage of great value to stock- 
men.^ 

The range of climate between the summits of the plateaus and the 
lower desert country of the canyon terraces and canyon bottoms is 
great indeed. The high precipitation of the Aquarius Plateau, for ex- 
ample, 25 to 30 inches, is chiefly in the form of snow which accumu- 
lates in the forest to a great depth. Settlers find it very difficult to live 
at an altitude over 7000 feet; their farms are usually found below that 
level where the climate is hot, arid, or semi-arid, and where irrigation 
is a necessity. From the cool, lake-besprinkled forests and meadows of 
the higher plateaus one looks down upon a country of extreme heat and 
dryness. The range of climate between the two situations is as great 
as one may find in most regions only by traveling through a considerable 
number of degrees of latitude, — a common range, however, in the great 
intermontane country between the Rockies and the Pacific Mountains. 

The range in climate between the Kaibab and the bottom of the 
canyon, for example, is as great as the climatic range between the moun- 
tains of Colorado and the Mohave desert. The winters on the Kaibab 
Plateau are extremely severe and from November until April the snow 
lies deep in the woods, often accumulating to a depth of 10 feet. Even 
in midsummer the nights are chilly and the days are cool. The winters 
in the depth of the canyon are mild, freezing temperatures are rare, 
and snow rarely falls below the level of the Esplanade (4500 feet), 
while snow never falls on the Tonto platform (2100 feet).^ 

In contrast to the cool summer days of the plateau is the intense 
heat of the entire canyon below the Red Wall. The bare rocks become 
so hot as to burn the hand, and by nightfall a wind like a furnace blast 

1 J. W. Powell, Lands of the Arid Region of the United States, U. S. Geog. and Geol. Surv., 
1879, pp. 98-103. See these pages for a more extended description of the tree species of the 
plateau province, their habitats and relative commercial importance at the time of Powell's 
surveys. 

2 J. W. Powell, Lands of the Arid Region of the United States, U. S. Geog. and Geo!. Surv. 
of the Rocky Mountain Region, 1879, p. no. 

3 Nokle, loc. cit. 



COLORADO PLATEAUS 289 

escapes through the canyon. But the heat is not enervating, for the 
relative humidity is very low and moisture is rapidly evaporated from 
the body. The bottom of the canyon is decidedly arid, for much rain- 
fall evaporates before it reaches the great depths. The Coconino Plateau 
on the south side of the canyon has a lesser altitude than the Kaibab 
Plateau, and while the latter is decidedly moist the former is semi- 
arid. Often no rain falls for a month at a time. In both cases there are 
distinct summer and winter maxima. Powell Plateau on the south- 
western border of the Kaibab has a high eastern portion, and a low 
western portion, and from end to end there is a transition in climatic 
conditions similar to the transition that is experienced in passing from 
the Kaibab to the Coconino Plateau. In wnnter it is a resort for game 
and wild horses driven out of the Kaibab by the snow. The higher 
eastern end has an abundant rainfall ; the lower western end is semi-arid. 

One of the finest forests of the whole region is found on the high and 
better- watered Kaibab. The trees of the Kaibab forest are mostly 
yellow pine, but at the higher elevations spruce also is common. 
Pines are found on the sunny slopes of the ravines, spruce on the shady 
slopes, and both grow only scatteringly upon the valley bottoms. These 
and the aspens are the three principal genera, but about the borders of 
the plateau are patches and scattered individuals of cedar {Juniperus 
occidentalis) , mountain mahogany {Cercocaspus ledif alius), and pinon.^ 

The influence of elevation upon vegetation through temperature and 
rainfall is admirably shown in the Grand Canyon, where it has been 
observed by Noble, from whose excellent descriptions the following 
paragraphs are taken ^ : 

"The surface of the Kaibab Plateau is covered with a magnificent open forest of yellow 
pine; the trees grow large and far apart and the ground is free from undergrowth, giving its 
surface the aspect of a great park; Engelmann spruces grow on the north slopes of the washes, 
and cottonwoods, aspens, and scrub oaks in their bottoms; a minor flora of flowering plants, 
exceedingly rich in species, covers the floor of the forest. The flora of the plateau surface or 
the south rim of the canyon differs completely from that of the Kaibab; it is covered with a 
forest of gnarled and stunted trees of juniper and piiion, with here and there a buckbrush bush; 
the trees never form thickets, but grow wide apart; while the open stretches are covered with 
sagebrush and mormon tea, with occasional cactus, mescal, and plants of the century family. 
This difference between the floras of the north and south rim is due to the differences in pre- 
cipitation and temperature, which vary directly with the altitude. For this reason the floras 
of the plateaus furnish an almost unfailing index of the elevation. This is beautifully shown 
on the southwestward-sloping surface of Powell Plateau, the whole eastern half of which lies 
at an elevation of from 7000 to 7500 feet and is covered with the open pine forest character- 
istic of the Kaibab. At about 7000 feet the character of the flora changes, and passes into the 

1 C. E. Button, Tertiary History of the Grand Canyon District, Mon. U. S. Geol. Surv., 
vol. 2, 1882, p. 132. 

2 L. F. Noble, Contributions to the Geology of the Grand Canyon, Arizona (The Geology 
of the Shinumo Area), Amer. Jour. Sci., vol. 29, 1910, pp. 374-380. 



290 FOREST PHYSIOGRAPHY 

gnarled and stunted forests of juniper and pinon characteristic of the southern plateau across 
the canyon. 

"Within the canyon itself the variation in the flora is just as great, and is again an index 
of the elevation. 

"The flora of the Esplanade platform, a thousand feet below the south rim, consi^sts of stunted 
bushes of juniper and pinon, with greasewood as the ground bush in place of the sagebrush of 
the Coconino Plateau. The cactus, mescal, and plants of the century family are present in 
greater abundance than on the plateau, but in less abundance and in more stunted develop- 
ment than in the bottom of the canyon. This is due to the fact that the Esplanade level is 
within reach of the winter snows and frosts. 

"The flora of the Tonto platform, three thousand feet below the south rim, and of all the 
interior of the canyon below the Red Wall, is the flora of a hot and arid desert in its most 
characteristic form. The dominant plants are the greasewood bush, the mormon tea, and the 
cactus. The mescal and the plants of the century family here attain their greatest develop- 
ment and size. The cacti are particularly rich in species. Every plant in the flora is either 
prickly or aromatic; leaf surfaces are reduced to a minimum; devices for storing water attain 
the greatest perfection; and the dominant color is a somber gray. The somber colors and the 
reduction of leaf surface are apt to deceive the observer, both in regard to 'the richness of the 
flora in species and the abundance of plant life, which is far greater than one would suspect. 
The only tree is the screw-mesquite, which grows in the beds of those washes that contain liv- 
ing or intermittent streams. 

"The vegetation in the bottoms of those canyons of the north side in the Shinumo Amphi- 
theater which contain living streams is beautiful beyond description, and in refreshing con- 
trast to the desert flora of the Tonto platform. Tall cottonwoods grow in the lower canyons; 
the walls are hung with maidenhair fern in the shady places; and willow thickets border the 
stream. Grass grows on the banks where there is soil. Higher up in the canyons, oaks, 
maples, and other deciduous trees come in, and often beds of tall rushes. The most character- 
istic bush of these upper north-side canyons is the manzanita, which does not grow on the 
south side of the Grand Canyon." 

In the northeastern or Grand River district there is a characteristic 
change in vegetation on ascending from the valley or canyon floors to 
the plateau summits. In the low valleys and on the dry ridges sage- 
brush occurs ; in the moist valleys are found willow, buffalo berry, service 
berry, and along the larger streams cottonwood. The quaking aspen 
requires more water and is found only above 7500 feet, on the plateau 
summits or in the vicinity of springs or on cool and moist slopes. All 
the low bluffs and ridges support some pinon and juniper of low height 
growth, yellow pine occurs infrequently, and what is locally called white 
pine (Abies engelmanni) is found only in some of the gulches and 
ravines leading down from the summit of the Book Cliffs.^ 

Mountains of the Plateau Province 

henry mountains 

The mountains of igneous origin that occur locally throughout the 
plateau country have been referred to in a number of preceding para- 
graphs in this chapter. Some of the most important features of the 

1 F. V. Hayden, U. S. Geog. and Geol. Surv. of the Terr., 1S76, pp. 68-69. 



COLtDRADO PLATEAUS 



291 







r / y r-: -r • -^^ 



> >-\ / 






>^ 



V-,* 











^ 



'-.:'''h<y\)< 1,1 '■' 



''i^,^',. of tliS 

C7 ■ VICINITY. ''I 



Fig. 82. — Relief map of the Henry Mountains, a group of eroded laccolithic domes in the plateau 
country, southeastern Utah. (Gilbert, U. S. Geol. Surv.) 

larger groups deserve a word of detailed explanation. Our first con- 
sideration will be the Henry Mountains, which, with the San Francisco 
and Mount Taylor groups, have been studied in more detail than others 
of their kind. 
The Henry Mountains are in southern Utah and are on the right 



292 FOREST PHYSIOGRAPHY 

bank of the Colorado River between the Dirty De\il and Escalante 
tributaries. They are a group of five individual mountains separated 
by low passes. Although they are in an arid region their height (7000 
to 11,000 feet) is such as to cause them to have a rainfall sufiicient to 
support forests. Mount Ellen is the highest of the five mountains and 
has a continuous crest line 2 miles long, with radiating spurs and bor- 
dering foothills. 

The Henry Mountains were formed by the intrusion of great masses of molten rock into 
surface beds in the form of a laccolith. The overarching strata that were lifted up as a conse- 
quence of the intrusion have been so extensively removed by erosion that there is now revealed 
the heart of the laccolith, and the displaced beds are exposed on the flanks and borders of the 
mountains for the most part. There is considerable diversity in the degree of erosion; some 
of the mountains are still largely covered on one or more sides by overlapping sedimentary 
rocks. 

The Henry Mountains in southern Utah stand upon a desert plain 
having a mean altitude of 5500 feet. A large part of the rain that 
falls in the region is distributed over the mountains, a fact that is re- 
flected in the distribution of the springs and the vegetation. On the 
surrounding plain the vegetation is extremely meager, grasses and 
shrubs and in favored localities the dwarf cedar {Juniperus occiden- 
talis). The highest peak of the group is Mount Ellen, 11,250 feet, 
which bears cedar about its base, pinon a little higher up, then yellow 
pine, spruce, fir, and aspen. The summits are naked; the upper un- 
timbered slopes are covered with a luxuriant growth of grasses and 
herbs. Of the forest growths noted the pines grow in a scattering man- 
ner, but the cedars and the firs are in dense groves.^ Among the other 
four mountains of the five comprising the group, Mount Pennell (11,150 
feet) reaches above timber line and has a forest growth similar to that 
on Mount Ellen except that the timber reaches almost to the summit; 
on Mount Hillers (10,500) the timber reaches to the principal summit, 
but is less dense than on the other higher mountains; Mount Ellsworth 
is so low (8000) that it bears none of the forest trees that grow on the 
others, its vegetation is cedar and pinon right to the summit, and the 
grasses are less rank and grow in scattered bunches; Mount Holmes 
(7775) has a similar growth except that a few spruce trees grow high 
up on the northern flank. 

Among the extinct volcanoes and associated lava flows Mount Taylor^ 
San Francisco Mountain, Sierra MogoUon or the MogoUon Mesa, the 
Panguitch Lake Buttes of Utah and the Marcou Buttes of New Mexico 
are important members. These have all been formed by the extrusion 

1 G. K. Gilbert, Report of the Geology of the Henry Mountains, U. S. Geog. and Geol. 
Survey of the Rocky Mountain Region, 1877, p. 118. 



COLORADO PLATEAUS 



293 



of lava in one or another form, either as volcanic mountains or as lava 
flows. Like the laccolithic mountains they have no range forms or 
structures. Their features are all grouped about centers of structural 
disturbance, and radiating slopes and spurs and drainage lines are the 
rule. They have the utmost differences of position with respect to 
timber lines. Many do not reach above the dry timber line, some do not 
reach the cold timber line, a few extend above the cold timber line and 
have unforested summits. Those having a forest cover at all are en- 
circled by a band of forest vegetation from the 7000 or 8000 foot level to 
the 11,000 foot level, which represents the upper limit of tree growth. 
In all of them there is a notable canting of the timber lines on passing from 
the warmer and drier southern slopes to the colder and moister northern 
slopes. The difference of level amounts in some instances to a thousand 
feet and is always several hundred feet, being lower on the northern 
slopes. This condition has been especially well described by Merriam.^ 
More recently Lowell has noted that the degree of canting increases 
with increasing altitude and appears to be a function of radiation and 
insolation as controlled by area. With increasing altitude there is de- 
creasing area. The two sides of a cone will therefore show increasingly 
greater differences in the limiting elevations of the tree zones and a 
more marked canting of the vegetation belts and timber lines. ^ 




Fig. 83. — Timber zones on San Francisco Peaks, Ariz., showing increase in the degree of canting with 
increasing elevation. (Lowell.) 

1 C. H. Merriam, Results of a Biological Survey of the San Francisco Mountain Region in 
Arizona, North Am. Fauna, No. 3, 1890. 

2 Percival Lowell, The Plateau of the San Francisco Peaks in its Effects on Tree Life, Bull. 
Am. Geog. Soc, vol. 43, 191 1, p. 380. 



294 FOREST PHYSIOGRAPHY 

SAN FRANCISCO MOUNTAINS AND MOUNT TAYLOR 
SAN FRANCISCO MOUNTAINS 

The San Francisco Mountains are the center of a volcanic field in 
northern Arizona that includes seven large peaks and several hundred 
small peaks. Cones and lava flows together cover about 2200 square 
miles of country. San Francisco Mountain, the highest peak in the 
group, rises to 12,700 feet above the sea and has 5000 feet of relative 
altitude. Other prominent peaks are Kendrick Mountain, 10,500 feet, 
and Bill Williams, Sitgreaves, Elden, and O'Leary mountains, which do 
not exceed 9500 feet. The smaller volcanic cones are scattered about 
irregularly and have great variety of topographic detail. The plateau 
about the base of these mountains and throughout the volcanic field 
maintains a greater altitude than elsewhere, a fact due to (i) greater 
initial height of the locality before volcanic activity began and (2) the 
protective influence of the hard lavas which have preserved the surface 
from that denudation which later brought the surrounding plateau to a 
lower level. 

San Francisco Mountain is a composite cone built up by the lavas and breccias of five dis- 
tinct periods of eruption. The chief vents of these periods are near each other, so that the 
total effect has been to give the mountain a symmetrical outline. The principal lavas are 
dacite, rhyoHte, and andesite. 

Twelve principal watercourses drain radially outward from the 
higher parts of the area. They are irregular in the lava fleld, but be- 
come more direct beyond the borders of the field, where deep canyons 
generally occur. After a cloud-burst or heavy shower water runs for a 
few hours in the canyons or washes within the limits of the storm area 
and then the channels become dry again. But one stream. Oak Creek, 
runs throughout the year; its more even plow is due to several large 
forest springs at its headwaters. In an area of 1000 square miles about 
San Francisco Mountain only about 25 springs and water pockets or 
"tanks" occur, and at least two- thirds of these are situated near the 
mountain, so that the surrounding country is extremely dry and difficult 
to traverse. The "tanks" and lakes which usuafly occur at the heads 
of the washes have a most variable supply as regards both quantity and 
quality. The lakes are due to the damming of the watercourses by 
lava flows. Some of them have become dry by the cutting down of 
their outlets and the accumulation of sediments; their floors are now 
grass- covered and picturesque glades. 

The soils of the San Francisco volcanic field vary from " adobe " 
soils of the floors of temporary lakes and ponds to the pervious cinder 



COLORADO PLATEAUS 



295 



and scoriaceous soils of the slopes of volcanic cones and ridges. Be- 
tween these two extremes are gravelly loams of several varieties moder- 
ately pervious to water and best adapted of all the soils to the growth 
of forests. The coarse cinder soils lose water so rapidly that they are 
extremely sterile, while the adobe soils crack open when dry and swell 
when wet and are not adapted to forest requirements.^ 

The San Francisco Mountains are encircled by barren plateau country, 
but they are themselves covered with a beautiful forest of juniper, pine, 





Fig. 84. — -Mesa forest of western yellow pine in the Mogollon Mountains near Iron Creek, Gila National 
Forest, New Mexico. (Photograph by DeForest.) 

and spruce. It surrounds the base of the mountains and stretches 
westward to the borders of the escarpment of the Colorado Plateaus 
and down it nearly to its foot. The forest accompanies the escarp- 
ment southwestward to the boundary of Arizona and extends in a north- 
west-southeast direction for over 200 miles. Its greatest breadth is 
opposite the San Francisco Mountains, where it is nearly 50 miles wide. 
Elsewhere its breadth is from 12 to 25 miles, thus giving it an area of 
from 12,000,000 to 23,000,000 acres. It is from all points of view the 
finest forest in the Southwest and is composed of an almost pure growth 
of yellow pine except in the higher altitudes of the San Francisco Moun- 

1 Leiberg, Rixon, Dodwell, and Plummer, Forest Conditions in the San Francisco Moun- 
tains Forest Reserve, Arizona, Prof. Paper U. S. Geol. Surv. No. 22, 1904, p. 15. 



296 FOREST PHYSIOGRAPHY 

tains. It is an open forest with little undergrowth and the trees are 
of good size for lumber purposes.^ 

The yellow- pine zone extends from 7000 to 8200 feet. Above it and 
between elevations of 8500 and 9800 feet and occasionally to 10,000 
feet is the transition forest type, composed principally of red fir, white 
fir, aspen, and a few Engelmann spruce. The subalpine forest type 
extends from 9S00 to 12,400 feet and is found only on Kendrick Moun- 
tain and San Francisco Peaks. It is composed of aspen, Engelmann 
spruce, etc. Above the subalpine forest is a treeless belt which is rep- 
resented only on and near the summit of San Francisco Peaks, Fig. 83.^ 

Below the yellow-pine zone and between 5700 and 6200 feet is a 
woodland belt where both climate and soil are very dry. Juniper and 
pinon are the chief species. They stand as a transition type of vege- 
tation between the desert sagebrush and the true forest of the next higher 
belt. 

MOUNT TAYLOR 

Northeast of the Zuni Plateau is Mount Taylor one of the most promi- 
nent volcanic elevations of the southeastern section of the province. 
The central mass and associated lava flows constitute the summit of a 
mesa whose base consists of sedimentary rock. The mesa is 47 miles 
long and has an extreme breadth of 23 miles, with an average altitude of 
about 8200 feet. Mount Taylor itself is 11,390 feet high. It is a lava 
cone principally and was a central pipe or vent from which the sur- 
rounding flows were derived. It is now very much eroded, though it 
still maintains a roughly amphitheatral form. It is heavily timbered 
and deeply covered with soil and talus. 

In the Mount Taylor district and east of the main volcano are many 
lesser volcanic elevations "now greatly denuded so that only the central 
core remains. They stand from 800 to 1500 feet above the general level 
of the plain as steep-sided sharp-crested buttes of great interest as the 
roots of once active volcanoes now all but swept away.^ 

Among the other areas of higher rehef in the Colorado Plateaus is 
Mogollon Mesa, a timbered plateau 7000 feet above the sea and extend- 
ing southward from the San Francisco Mountains (Plate II). Limestones 
and shales form the basement rock upon which the basaltic lavas that 

1 Henry Gannett, igth Ann. Rept. U. S. Geol. Surv., 1897-98, p. 47. 

2 Leiberg, Rixon, Dodwell, and Plummer, Forest Conditions in the San Francisco Mountains 
Forest Reserve, Arizona, Prof. Paper U. S. Geol. Surv. No. 22, 1904, pp. 18-19. 

' C. E. Button, Mount Taylor and the Zuiii Plateau, 6th Ann. Rept. U. S. Geol. Surv., 
1884-85, especially Panorama in the Valley of the Puerco, Plate 21, p. 171; also D. W. Johnson, 
Volcanic Necks of the Mount Taylor Region, New Mexico, Bull. Geol. Soc. Am., vol. 18, 
1907, pp. 303-324- 



COLORADO PLATEAUS 297 

constitute the mass of the mountains have been distributed. These 
strata dip northward and their edges are exposed on the southern border 
of the district where the lava cap has been most extensively frayed by 
dissection, Fig. S^. Here the main margin of the elevation consists of long 
lava-capped promontories of the plateau fronted by a series of detached 
remnants in the form of mesas and buttes. The mountains have been 
extensively dissected and present a bold and varied relief in contrast to 
the more regular margin of the mesa above which the mountains rise as 
from a pedestal. Thrifty forests of yellow pine cover both the mesa 
and the higher slopes and owe their existence to the favorable tem- 
perature and rainfall induced by the elevated position of the moun= 
tains on the windward border of the plateau country.^ 

1 Wheeler Surveys, Geology, vol. 3, 1875, PP- 217-587. 



CHAPTER XVIII 
ROCKY MOUNTAINS. I 

Northern Rockies 
boundaries and subdivisions 

Between the sensibly flat and only slightly dissected basalt plains of 
the Columbia River and Snake River regions and the almost equally 
flat Great Plains of Montana is a broad belt of wild, rugged, mountain- 
ous country composed of many northward- and northwestward-trend- 
ing mountain ranges. Though several transcontinental railway lines 
cross the region and occasional valleys, as the Bitterroot, are rather 
thickly settled, the forested mountain slopes and the higher ranges 
have few trails and fewer roads, and are almost unknown except to 
the hunter and the explorer.^ 

The chief members of the northern part of the Rocky Mountain 
System^ in the United States are the Lewis and Livingston ranges, which 
form the eastern and front members of the system in northern Montana; 
the Galton, Flathead, Purcell, Cabinet, and other ranges east of the 
continental divide; the central Bitterroot Mountains on the boundary 
between Montana and Idaho; and the Clearwater, Salmon River, Priest 
River, and Coeur d'Alene mountains on the west, Fig. 86. The close 
proximity of these ranges to each other, in general their similar align- 
ment and their common participation in certain important events in 
the physiographic history of the region, are conditions which form an 
adequate basis for the common association of the separate units under 
the group name of the northern Rockies of the United States; but 
there are wide differences in local detail, in the quality of the moun- 
tain slopes, the length and disposition of transverse valleys, and the 
degree of dissection which the individual ranges have suffered. It there- 
fore becomes necessary to distinguish the essential elements of form and 
the limits of each unit in the system. 

1 F. C. Calkins, A Geological Reconnaissance in Northern Idaho and Northwestern Mon- 
tana, Bull. U. S. Geol. Surv. No. 384, 1909, p. 12. 

2 The United States Geographic Board makes the term Rocky Mountain System embrace 
the whole of the mountainous region between the Rio Grande and the 49th parallel, specifi- 
cally the ranges of western Texas, New Mexico, Colorado, Wyoming, Idaho, and Montana. 
In this book the Trans-Pecos Highlands are set ofif as a separate province. (See p. 3S7.) 

208 




Fig. 85. — Mountain systems and ranges and intermontane trenches, northern Rockies. 
(Ransome, U. S. Geol. Surv.) 




Fig. 86. — Location map of a part of the Northern Rockies. 



300 FOREST PHYSIOGRAPHY 

In naming and describing the different mountain ranges of the north- 
ern Rockies that cross the international boundary line it has been pro- 
posed that a double and purely topographic principle be employed, the 
principle of the continuity of crest lines and the positions of, the majoi 
erosion valleys.^ Erosion troughs or intermontane trenches are here 
the natural lines of demarcation between the different ranges, for they 
have a highly exceptional and remarkable development on a great 
scale. 

INTERMONTANE TRENCHES 

In respect of size the major valleys of the region are often qmte out 
of proportion to the streams that now drain them; the longest depression 
in the whole system is occupied by relatively small streams, the head- 
waters of the Kootenai, Columbia, Frazer, and others. They have 
steep though seldom precipitous walls, and rather flat, lake-dotted 
floors. They are called intermontane or valley trenches. It is certain 
that they had their direction determined in many cases primarily by 
fault lines or zones, so that some of them, for example Kootenai Valley, 
mark the boundary between different rock formations. They have 
probably been brought to their present form chiefly by the long-con- 
tinued erosion of valley glaciers powerful enough to override the divides 
between the heads of the larger streams and to degrade them to a 
common level. - 

In this connection it is in point to indicate that valley glaciers of 
great size supplied by many headwater tributaries are much more 
powerful agents of erosion in effecting topographic discordances such 
as appear in the hanging valleys and the mountain slopes adjacent 
to steep-sided U trenches, and in opening up valleys such as these 
trenches are to-day, than are continental ice sheets. A continental ice 
sheet is spread over the entire surface, and though it may erode to 
some extent differentially there is no such concentration of ice action- 
as is the case in a region of heavy alpine glaciation. The valleys of 

1 R. A. Daly, The Nomenclature of the North American Cordillera between the 47th and 
Ssd Parallels of Latitude, Geog. Jour., vol. 27, 1906, pp. 586-606. This excellent paper out- 
lines the difficulty of understanding the mountain nomenclature of the Rockies, and on pages 
589 and 590 summarizes the various names applied by prominent authorities to the Rocky 
Mountains. In all at least 26 different names have been employed. It is suggested that 
greater differentiation be aimed at in designating the various members of the Rocky Mountain 
system. It is also noted that the authorities variously designate the terminal points of the 
different mountain ranges (pp. 592-593). The nomenclature is still further confused owing to 
the fact that some atlases and map sheets give different titles to the same range. 

2 F. C. Calkins, A Geological Reconnaissance in Northern Idaho and Northwestern Mon- 
tana, Bull. U. S. Geol. Surv. No. 384, 1909, p. 32- 



ROCKY MOUNTAINS. I 30 1 

Lake Chelan, the Okanogan, and the Coeur d'Alene are illustrations. 
In all three instances there are extensive catchment basins which fed 
prodigious glaciers. 

Among the eleven longitudinal valleys or intermontane trenches which 
serve as convenient lateral boundaries for the members of the Pacific 
Cordillera are four of first rank; three of these occur in the northern 
Rockies, and lie west of the front ranges, the Purcell range and the 
Selkirks respectively. Each is designated a " trench," and as so used the 



Horizontal Scale 



12 3 4 Smiles 

(Vertical Scale but slightly exaggerated) 
Fig. 87. — East-west section, showing flat floor and steep bordering slopes of a typical intermontane 
trench. (Data from Coeur d'Alene quadrangle, U. S. Geol. Surv.) 

term means "a long, narrow, intermontane depression occupied by two 
or more streams (whether expanded into lakes or not) alternately drain- 
ing the depression in opposite directions."^ The easternmost and much 
the longest of the series of trenches is the wide valley occupied at the 
international boundary by the Kootenai River." It extends from the 
southern end of Coeur d'Alene Lake northward to Liard River in British 
Columbia, about 900 miles, and throughout it has the form of a narrow 
and remarkably straight depression lying between the easternmost mem- 
ber of the Rocky Mountains and the rest of the system. This depression 
is unique among all the mountain valleys of the earth for its remarkable 
persistence. It is not drained by a single great river, but is occupied in 
turn by the headwaters of the Flathead, Kootenai, Columbia, Canoe, 
Frazer, Parsnip, Finlay, and Kachika rivers. The name Rocky Moun- 
tain trench is now applied to it. 

The major valley next in order to the west is occupied at the bound- 
ary by that portion of the Kootenai River that returns into Canada 
after rounding the great bend at Jennings, Montana. This trench 
begins on the south near Bonners Ferry, Idaho, and is occupied north 
of Kootenai Lake by the Duncan River. In line with the Duncan River 
Valley is the 50-mile trough occupied by Beaver River which enters 
the Columbia at the Canadian Pacific Railroad crossing. The length 
of this topographic unit, called the Purcell trench, is about 200 miles. 

The third major trench is known as the Selkirk trench or the Selkirk 

1 Daly, loc. cit., p. 596. 

2 F. L. Ransome, Geology and Ore Deposits of Coeur d'Alene District, Idaho, Prof. Paper 
U. S. Geol. Surv. No. 62, 1909, p. 13. 



302 FOREST PHYSIOGRAPHY 

Valley, and is occupied southward by the Columbia River. Its north- 
ern extremity is near the 5 2d parallel, where it is confluent with the 
Rocky Mountain trench. The southern end of the trench is about 
60 miles south of the 49th parallel, where the Columbia River enters 
the great basalt plateau of Washington. 

Besides these three first-rank valleys or trenches in the northern 
Rockies are a number of second-rank longitudinal trenches. Waterton 
River, Flathead River, and Zigzag River occupy parallel valleys that 
still further divide the northern Rockies into the Lewis, Livingston, 
MacDonald, and Galton ranges. Cross trenches or valleys are employed 
in indicating the minor subdivisions of the principal mountain systems 
and ranges, as the Slocan Mountains are separated from the rest of 
the Selkirk System by a depression occupied by Slocan River, Slocan 
Lake, and the valley of a creek whose mouth is at Nakusp or Arrow 
Lake.^ In a similar way cross valleys divide the Colville Mountains, 
Pend Oreille Mountains, etc., from the larger ranges. 

GEOLOGIC FEATURES 

The detailed topographic qualities of the northern Rockies as dis- 
cussed in succeeding paragraphs may be better understood by a 
brief consideration of certain fundamental geologic conditions. From 
Kootenai River or Purcell trench westward to the Columbia there is a 
much disturbed, highly folded, rock complex in which the metamor- 
phism of the sediments generally diminishes- in intensity westwardly.^ 
To this metamorphosed complex the rocks east of the Purcell trench are 
in striking contrast. They consist of a thick series of arenaceous sedi- 
ments (pre-Cambrian) which show no pronounced regional rnetamor- 
phism. The essential structural features are open folding and exten- 
sive faulting. They are known to extend from the Belt Mountains 
westward to the Purcell trench. Some of the ranges (Purcell, Cabinet, 
Coeur d'Alene, Livingston, and Lewis) are composed almost entirely of 
this group of rocks. In central Idaho the same strata are invaded, 
displaced, and probably for the most part cut off by a great granite 
batholith.^ The most striking structural feature of the western part of 
the sediments east of the Purcell trench is of course the existence of 
great faults of northwest trend that determine the courses of the trenches 
and rivers and block out the individual mountain ranges. 

1 Daly, loc. cit., p. 599. 

= Ransome and Calkins, Geology and Ore Deposits of the Coeur d'Alene District, Idaho, 
Prof. Paper U. S. Geol. Surv. No. 62, 1908, p. 16. 

' W. Lindgren, A Geological Reconnaissance across the Bitterroot Range and Clearwater 
Mountains in Montana and Idaho, Prof. Paper U. S. Geol. Surv. No. 27, 1904, p. 16. 



ROCKY MOUNTAINS, I 



303 




Fig. 88. — Coeur d'^Mene Aluuntains, looking from above Wardner. Shows the mature dissection of a 
plateau-Iike uplift. (Ransome and Calkins, U. S. Geol. Surv.) 




Fig. 89. — Cceur d'Alene Mountains, looking toward the crest of the range, from valley of South Fork 
of Cosur d'Alene River. Shows characteristic equality of ridge lines. (U. S. Geol. Surv.) 



304 FOREST PHYSIOGRAPHY 

CCEUR d'aLENE range 

The Coeur d'Alene range, rudely triangular in outline, extends from 
Lake Pend Oreille on the northwest, southeastward to Lolo Pass (lat. 
46° 36' on the continental divide between Idaho and Montana). '^ Its 
southern boundary is vague but should probably be considered as cor- 
responding to the divide on the northern border of the Clearwater drain- 
age basin, Fig. 86. Its western margin adjoins the Columbia Plateaus; 
its eastern boundary is constituted by the valleys of Clark Fork, Flat- 
head River, and Jocko Creek. The Cceur d'Alene range, Fig. 89, appears 
as a rather monotonous expanse of ridges nearly equal in height and with 
somewhat level crests that do not bear prominent summits.^ Its broad 
aspect is that of a maturely dissected plateau, whose general level in its 
central and highest part is a little above 6000 feet. The rough equality 
of summit levels becomes less marked toward the west, dissection having 
there progressed so far that the original regularity of level has now been 
almost lost. It is tentatively concluded that this topographic uniformity 
depends upon former base-leveling, but much further w^ork is required 
for a complete demonstration. 

The Cceur d'x\lene region had been folded and faulted into essentially its present structure 
and its topography had been developed by probable base-leveling, uplift, and extensive and 
deep dissection to essentially the present conditions by the time the great Miocene lava flood 
occurred, for great quantities of basalt flowed up the existing valleys. This fact for example 
explains Coeur d'Alene Lake, which occupies a large valley that was partly filled with basalt 
and afterward recut by the original river, thus leaving terraces of basalt on the older slopes. 
Later a deposit of Pleistoijene gravels dammed the valley on the north, originated the lake, and 
gave it approximately its present outline, backing up the waters of Coeur d'Alene and St. Joseph 
rivers. 

PRIEST RIVER RANGE 

The Priest River range south of the international boundary and east 
of the Pend Oreille range has been deeply sculptured by glaciers and 
streams, so that canyons, cliff-bordered cirques, and narrow ridge crests 
are common. The rocks of the range consist principally of highly 
fissured granite and syenite; a certain amount of slate and gneiss occurs 
at the southern end. The average altitude of the range is 5000 to 6000 
feet, with a number of elevations attaining 8000 feet. The irregularly 
fissured condition of the granites results in the better retention of the 
precipitation than is the case in the schistose rocks of the Pend Oreille 
range. The latter are either water-tight or else afford too rapid drain- 
age, depending on the dip of the planes of schistosity. About 91 % of 
the total forest in the Priest River National Forest is white pine and 

1 W. Lindgren, Prof. Paper U. S. Geol. Surv. No. 27, 1904, p. 23. 

2 F. C. Calkins, A Geological Reconnaissance in Northern Idaho and Northwestern Mon- 
tana, Bull. U. S. Geol. Surv. No. 384, 1909, p. 14. 



ROCKY MOUNTAINS. I 



305 



tamarack; yellow pine is found below 3500 feet, white pine between 2400 
and 4800 feet (best development between 2800 and 3500 feet), and the 
subalpine fir, of little economic importance, grows above 4800 feet.^ 



CABINET RANGE 



This range extends from Bonners Ferry southeastward to the junction 
of Jocko Crsek and Flathead River. Its western border is definitely 
marked by the Purcell trench and its southwestern border by the nearly 
straight valley occupied chiefly by Clark Fork, Columbia River, and 




1 J4 1 



2 3 4 5 Kilometeia 
val DOO feet 



Fig. go. — Southern end of the Cabinet Mountains, Idaho. The depression on the right is part of a 
typical intermontane trench. (Sandpoint quadrangle, U. S. Geol. Surv.) 

Flathead River. The eastern border is constituted by the valley of Little 
Bitterroot River, a short section of Flathead River, and Fishers Creek. 

As a whole the Cabinet range is somewhat loftier than the Coeur 
d'Alene range and far more diversified in character. The eastern part 
is a dissected plateau, but the quality of the dissection is markedly 
different from that in the Coeur d'Alene Mountains, for the differ- 
ences in the hardness of the rock are so pronounced and the region has 
been so deeply scored by rivers and so intensely glaciated that its 

1 J. B. Leiberg, Priest River Forest Reserve, 19th Ann. Rept. U. S. Geol. Surv., pt. 5, 1897- 
98, pp. 21S-224. 



3o6 FOREST PHYSIOGRAPHY 

details of sculpture are highly picturesque. The eastern portion of the 
Cabinet range has a number of prominent mountain peaks and a deeply 
serrate sky line in striking contrast to the lower, even-crested ridges 
toward the west. Some of the peaks are composed of resistant quart- 
zite and overlook many great steep-walled amphitheaters or glacial 
cirques developed upon their northern, eastern, and western slopes. In 
the northern cirque of Bear Peak (8500 to 9000 feet) a small glacier 
may be found to-day, a remnant of those larger Pleistocene glaciers 
that once flanked all the higher peaks of the region and gave rise to 
cirques and other glacial features.^ 

PURCELL RANGE 

The Purcell range trends north-northwest and is for the most part 
bounded on the east by the Rocky Mountain trench and on the west by 
the Purcell trench; the rest of its boundary is defined by the valley 
of Kootenai River. The greater part of the range is in Canada; only 
the southern end projects into the United States and is embraced in 
the great bend of the Kootenai. The section south of the boundary 
is divided into three subdivisions by Mooyia (west) and Yaak (east) 
rivers. Five miles south of the international boundary the western- 
most range is crossed by a remarkably flat-bottomed, low-grade valley 
or trench, one of the many of its kind in the region. The crests of the 
ridges are comparatively even in height and have no conspicuous peaks. 
The mountains occupying the interstream area between the Mooyia 
and Yaak rivers are for the most part of gentle profile and are heavily 
wooded except where they have been swept by forest fires. The main 
divide is a rocky ridge bearing Mount Ewing just south of the bound- 
ary, besides a group of jagged summits (7500) at the southern end of 
the chain.^ The easternmost mountain ridge has the same general 
character as the main central ridge west of it. 

Among the other mountain ranges of the boundary section of the 
northern Rockies are the Pend Oreille on the west and the Flathead 
and the rugged Mission ranges on the east. These mountains have 
not been explored to any extent and generalizations concerning them 
would be too broad to be of any practical value. The easternmost 
ranges of the region are the Lewis and Livingston ranges, which form 
the sharp western boundary of the Great Plains. These have been 
studied with more care than the ranges west of them and may be dis- 
cussed in greater detail. 

J Calkins and McDonald, A Geological Reconnaissance in Northern Idaho and North- 
western Montana, Bull. U. S. Gaol. Surv. No. 384, 1909, p. 15. 
• Idem, p. 16. 



ROCKY MOUNTAINS. I 307 

LEWIS, LIVINGSTON, AND GALTON MOUNTAINS 

The Lewis and Livingston mountains in western Montana constitute 
the front ranges of the Rocky Mountains in that state and a part. of 
the adjacent province of Alberta. They consist in the main of strati- 
fied rocks of Algonkian age; igneous rocks occur but sparingly. The 

A*"^ A c<- „ , Ridge, northwest -. . , ,,. 

'\:r„J'^S^>S^ <^° Flat top Mtn.'"'—- ^^f.^~i=i==-»~--!:i^i^^^ 

Drift tliiis fauiiiy^^ '" /- ■*> ^ — -J^-^''''"!;,*:^-:::;/-'-"^;!!-^^ ^—--^^ T^^"^ Kennedy 

Creek 




12 3 

Fig. 91. — Topographic and structural section across the front ranges in Montana. (Willis.) 

strata are disposed in the form of a broad, northward or northwest- 
ward trending, well-defined syncline between two marginal and poorly 
defined anticlines. The northeastern margin — the Lewis Mountains — 
fronts the Great Plains; the southwestern margin — the Livingston 
Mountains — is in part eroded, and in part downfaulted by a normal 
fault (North Fork Valley). The valleys and ridges of both ranges are 
closely related to the syncline and anticlines thus defined. 

The eastern border of the Lewis range is an overthrust fault; Algon- 
kian strata have been moved northeastward over Cretaceous strata on 
the plane of the fault; the displacement on the thrust surface is not 
less than 7 miles, and the vertical movement is estimated at 3400 feet 
or more. It is to the upward movement on the fault plane that the 
Lewis Range owes its present elevation above the Great Plains, and, to 
a large degree, the abruptness of its eastern border.'^ 

The eastern margin of the Lewis range is deeply sinuous and is 
marked off from the Great Plains by cliffs of prodigious size. The crest 
of the range is everywhere narrow and in many places is "a knife-edge 
of jagged rocks." The precipices are frequently more than 1000 feet 
high and in some instances have an altitude of 4500 feet, with a slope that 
is nowhere below 50°, Fig. 92. These cliffs are the walls of profound 
amphitheaters which enclose small mountain basins commonly occupied 
by lakes. The elevations of the highest summits range from 85 00 to 

1 Bailey Willis, Stratigraphy and Structure, Lewis and Livingston Ranges, Montana, Bull. 
Geol. Soc. Am., vol. 13, 1902, pp. 307-308. 

The eastern border of the Rocky Mountains near the common border of British Columbia 
and Alberta is also marked by the presence of a great overthrust fault, the continuation north- 
ward of the fault at the eastern border of the Lewis Mountains. It runs north by west as 
indicated on the map of part of Alberta and British Columbia by Dowling. (D. B. Bowling, 
Cretaceous Section in the Moose Mountain District of Southern Alberta, Bull. Geol. Soc. 
Am., vol. 17, 1906, pp. 295-302.) 



3o8 



FOREST PHYSIOGRAPHY 




10,400 feet; the elevations of the wind gaps are from 5400 to 6000 
feet. 

The Livingston range extends from Mount Heavens north of Mc- 
Donald Lake northwestward to Mount Head in British Columbia. It 
lies west of the Lewis range in the United States, but the latter range 
ends near the international boundary and in Canada the front range is 



ROCKY MOUNTAINS. I 



309 




c > 

O I- 

f^ 3. 



^ c/5 

c 2 

.S£ 3 

& o- 
1) 

1-J o 

a. 

^ =^ 



310 FOREST PHYSIOGRAPHY 

the Livingston. The main continental divide follows the Livingston 
range for some distance southward of the boundary, descending to Flat 
Top Mountain and finally to the Lewis range, which it follows southward 
to latitude 46° 45'. Like the Lewis range the Livingston is often nar- 
row and presents massive mountain peaks of pyramidal outline. Deep 
valleys diversify its western slope and contain long narrow lakes which 
vary in length from two to ten miles. The lakes are bordered by slopes 
of gravel or talus, except at their heads, where cHffs rise precipitously 
to the range summits. The western limit of the Livingston Moun- 
tains is definite, but it has the aspect of a bold mountain face rising 
from foothills rather than the almost sheer face' of the eastern margin 
of the Lewis Mountains rising abruptly from the plains. 

The Lewis and Livingston ranges are characterized by the dominant 
influence of structure on altitude. In the northern part of the Lev/is 
range and in the Livingston range the greatest altitudes are in gen- 
eral related to the two anticlines; the master valleys are in the inter- 
vening syncline, and Flat Top Mountain is the former floor of a broad 
synclinal valley. A peneplain was formerly developed over the Great 
Plains and over the Galton range. On the soft rock of the plains it was 
well developed, but on the harder rocks of the Galton Mountains it was 
probably imperfect. In the Lewis range it is notable that each peak 
approaches in height that of its neighbors which stand along the strike 
in a similar structural position. However in a broad view and taking 
the Lewis and Livingston ranges as a unit, -no general upper limit of 
heights common to widely distributed peaks may be discerned. If the 
base-leveled surface was ever in existence in the range, the extreme 
localized deformation of the mountains has so warped the ancient 
surface, and intense erosion by both water and ice has so completely 
dissected it, as to make its determination very difficult if not impos- 
sible. 

It is truly remarkable how abruptly the wxU-developed and but 
little dissected peneplain of the Great Plains of Montana terminates at 
the foot of the front ranges. The line is almost as definite as a shore. 
The long-continued erosion which the peneplain represents must have 
affected the present mountainous area west of it, but was probably 
offset by repeated deformation terminating or culminating in the great 
overthrust to which the present mountain height and the deep dissection 
are largely due. In the Galton range the old surface may be safely in- 
ferred; the older features have not been so completely destroyed owing 
to the relatively small amount of local deformation and the less intense 
action of water and ice. For the Galton range, although bounded by 



ROCKY MOUNTAINS. 



311 




1 Yi 



10 12 3 15 Kilometers 
Contour interval 500 feet 



Fig. 94. — Map of a part of the Lewis Mountains, western Montana, representing typical glacial features 
of the range. (Chief Mountain quadrangle, U. S. Geol. Surv.) 



312 FOREST PHYSIOGRAPHY 

structural limits, is internally, but a simple uplifted block whose minor 
flexures or faults are not sufficiently pronounced to interrupt the ancient 
surface. 

GLACIAL FORMS 

Some of the most remarkable erosion features produced by alpine 
glaciers are to be found in the Lewis range on the continental divide in 
western Montana. They are represented on the Chief Mountain quad- 
rangle, Montana, Fig. 94, one of the most interesting topographic sheets 
yet published, not only because of the exceptional nature of the region 
but also because of the unusual faithfulness with which the topographer 
has represented the landscape. The strata of the Lewis Mountains are 
strongly jointed, a quality which is highly favorable to the plucking 
action of glacier ice; furthermore they lie nearly flat and boldly overlook 
the adjacent plains: a set of conditions exceedingly favorable for the 
development of glacial forms on an unusual scale. 

Three major topographic features are apparent in the region: (i) numer- 
ous reversed slopes occupied by lakes and lakelets; (2) strikingly deep 
wall-like valley sides; and (3) huge amphitheatral valley heads in 
which a number of living glaciers are to be found. All these features 
are normally associated with the work of alpine glaciers whose former 
existence in large numbers has also been determined by the familiar 
phenomena of eroded and plucked rock surfaces, terminal and lateral 
moraines, and hanging tributary valleys. Former glaciers plowed down 
all the main valleys and built up morainic accumulations which at 
Blackfoot and Browning, p. 412, merge into the terminal deposits of 
one of the great continental ice sheets. 

An examination of the valley systems in plan shows a remarkable 
degree of headward cutting on the part of the glacier ice. The amphi- 
theatral valley heads or alcoves on opposite sides of a divide have in 
many instances cut back to the point where a knife-like ridge has been 
formed, as south of Gould Mountain and on the continental divide two 
miles south of Chaney glacier. The process has resulted in the for- 
mation of pyramidal mountains such as Going-to-the-Sun Mountain, 
Cataract Mountain, Little Chief Mountain, Heavens Peak, and others, 
or in the formation of skeleton mountains of irregular outline such as 
Almost- a-dog Mountain, Appekunny Mountain, and Merritt Mountain. 

The manner in which such headward cutting has taken place has been 
well set forth by Johnson,^ who has observed that in glaciated mountains 
the great curving bergschrund of the snow-field penetrates to the foot 

1 D. W. Johnson, The Profile of Maturity in Alpine Glacial Erosion, Jour. Geo!., vol. 12, 

1904, pp. 569-578. 




Fig. 95. — Mount Gould, Lewis Range, Montana, looking southwest from South Fork of Swift Current. See Fig. 86 for 
location. Characteristic cliff of limestone overlooking argillite. The dark band is intrusive diorite. The valley head is 
a glacial amphitheater developed along joint planes. It is 4670 feet from lake to summit. (Willis.) 

313 



314 FOREST PHYSIOGRAPHY 

of the precipitous rock slope constituting the wall of the amphitheater 
enclosing the snow-filled cirque. He concludes that a causal rela- 
tion determines the coincidence in the position of the bergschrund and 
the foot of the cliff wall. The opening allows air to come irito contact 
with both ice and rock at the bottom of the crevasse. By day there is 
thawing, by night freezing, and blocks of rock are wedged off and the 
cirque wall riven. The bottom of the crevasse is therefore a "narrow 
zone of relatively vigorous frost-weathering." The result is a sapping 
of the foot of the cirque wall and its gradual steepening and retreat. 

The continuance of this action steepens the slopes of the glacial 
amphitheaters and pushes them back until the slopes on the open sides 
of the divide meet. Thus a more or less rounded divide such as may 
be found a few miles southwest of Point Mountain, at Flat Top Moun- 
tain, and other places, was destroyed, the mountain top was reduced to a 
pinnacle or needle and the divide to a sharp crested arete. It is this 
action which appears to have taken place in the Lewis range, and to 
the varying degrees to which the basal sapping was carried may be 
attributed the variation of mountain forms ranging between pinnacles 
on the one hand and fiat-topped mountains with small bordering 
cirques on the other. An extreme case of such extension of headwater 
amphitheaters may be seen in the Hayden Peak quadrangle representing 
a portion of the Uinta Mountains of Utah. In this case the amphi- 
theatral walls have been pushed back to the point where only skeleton 
ridges remain, and in one instance at least, as-west of Hayden Peak, the 
di\ide has been almost completely obliterated, so that the snow-fields 
on opposite sides must have been confluent during the glacial period. 

It may readily be inferred from these considerations that cirques 
may be (a) but slightly developed and the present expression of the 
mountains closely resemble the preglacial expression; or (b) they may 
be so extensively developed that the upland or mountain region in which 
they were formed has a fretted appearance; or (c) the cirques may be 
developed headward to a still greater extent and the dividing ridges 
trimmed to a row of serrate peaks or skeleton ridges. Further con- 
trasts in the present characters of the cirques will depend upon the 
amount of postglacial cutting or filling that has taken place. Most 
cirques as left by the ice contain but little loose material. Whether or 
not loose material is now present will depend upon the friability of the 
rock, the steepness and height of the cirque walls, the precipitation, etc. 
In the Lewis Mountains the cirques are especially well preserved and 
still exhibit, Fig. 94, great expanses of little-modified cirque wall, lakes 
of considerable size and number, and expanses of bare, glaciated rock. 



ROCfCY MOUNTAINS. I 315 

Concentrated sapping at the foot of the cirque wall results not only in headward retro- 
gression but also in downward excavation, and with the melting of the glacier on account of a 
warmer period the reversed slope at the foot of the cirque wall is occupied by a lake. It will 
be noted on the Chief Mountain sheet, Fig. 94, that lakes commonly occur in this position. 
Lakes are also commonly found some distance down valley where tributary glaciers have caused 
local overdeepening or the bottoms of the glacial channels and the production of reversed 
slopes back of which the present drainage is impounded. A third group of lakes is frequently 
found some distance down valley where the drainage has been blocked by morainal accumu- 
lations that mark the former limit of glacial ice. 

The valley sides and bottoms in this region usually bear one, two, or 
more terraces. The lower ones represent a valley filling which the 
streams are at present cutting away. The higher ones represent inter- 
rupted valley widening in horizontally bedded rock.^ 

The mountain valleys of these ranges are all noted for their steep walls 
and lake-dotted and rather fiat floors. Their forms are chiefly the 
result of earlier glacial action. The main glaciers were wide and thick 
and eroded their channel floors below the channel floors of their tribu- 
taries. Upon the disappearance of a glacier the former glacial channel 
became a large part or all of the present valley. Hence the character- 
istic features of the glaciated valleys and the hanging condition of their 
tributaries. (See Figs. 96, 97, and 98.) , 



GALLATIN, MADISON, JEFFERSON, AND BRIDGER RANGES 

In southwestern Montana is a group of mountains whose most 
important members are the Gallatin, Madison, Jefferson, and Bridger 
ranges. A small part of the southern end of the Madison range and 
the greater part of the northern end are composed of gneiss. The 
central part of the range is an immense laccolith, the uplift due to 
intrusion having carried portions of the sedimentary rocks almost 
to the summit of the range and overturned, broken, and changed the 
strata along the western and northwestern edges of the range, causing 
a varied and highly irregular topography. The Jefferson range con- 
sists in the north largely of granitic rocks. The southern section is 
divided into two parts; the eastern is plateau-like in character, the 
western is a monocline in which the sedimentary rocks are overturned 
to greater or lesser degrees from place to place. The Bridger range 
also consists of three sections, the southern extension being an over- 
turned monocline of stratified beds that rest upon gneisses which form 
the western spurs and foothills and also a large part of the main moun- 

1 Bailey Willis, Stratigraphy and Structure, Lewis and Livingston Ranges, Montana, Bull. 
Gaol. Soc. Am., vol. 13, 1902, p. 310. 



3i6 



FOREST PHYSIOGRAPHY 




Fig. 96. — A normally eroded mountain mass not affected by glacial erosion. (Davis.) 



Fig. 97. — The same mountain mass as in Fig. 96, strongly affectedby glaciers which still occupy its 

valleys. (Davis.) 




Fig. gS. — The same mountain mass as in Fig. 97, shortly after the glaciers have melted from its valleys. 

(Davis.) 



ROCKY MOUNTAINS. I 317 

tain mass. The overlying stratified beds form a sharp crest with peaks. 
The central portion of the range is composed chiefly of sedimentary 
beds and gneisses are absent. The northern section is also composed 
of stratified beds of sandstones, shales, and limestones which curve 
around the ends of the range. 

The Gallatin range is plateau-like at its summit and is composed 
largely of volcanic breccias which dip eastward and have their greatest 
elevations, about 10,000 feet, along the western border. Mount Black- 
more, one of the most prominent peaks of this range, rises to a height 
of 10,196 feet. 

During the general elevation of the region in which these mountains 
occur the strata were folded and eroded (Cretaceous) and lakes, some 
of them of great extent, were formed in enclosed fresh-water basins. 
The lake period lasted for a long time (Neocene to Pleistocene), and 
during the earlier part of the period there was tremendous volcanic 
activity. Great quantities of volcanic dust were carried hither and 
thither by the winds and at length deposited in part on the lake floors 
as white dust beds; deposition of vast amounts of dust took place upon 
the adjacent land surfaces, whence the deposits were later washed in large 
part into the lakes. Later cutting down of the lake outlets allowed 
these water bodies to become drained and the lake beds themselves to 
be dissected. The last phases of volcanic activity in the region were 
flows of basalt and rhyolite, and these now form the summits of mesas, 
as in the southern part of the Three Forks district.^ 

The last geologic episode which has had an influence on the topog- 
raphy and drainage of the district has been glaciation, but the glaciers 
were local and the drift deposits in the valleys are of local origin. The 
low elevation of the ranges, 7000 to 10,000 feet, did not allow vigorous 
glaciation, and glacial forms have weak expression except in a few favor- 
able localities. 

MINOR RANGES OF WESTERN MONTANA 

In western and southwestern Montana is an extensive area hemmed in 
by the Madison, Jefferson, and other ranges on the south and the Lewis, 
Livingston, and other ranges on the north. On the east it extends to 
the Big Belt Mountains, on the west to the Bitterroots, Fig. 86. The 
tract includes no prominent mountain chains, only short ranges which 
reach up to a more or less common level. The geologic conditions are 
somewhat complex, the rocks consisting of greatly deformed sedimen- 

1 A. C. Peak, Three Forks Folio U. S. Geol. Surv. No. 24, 1896, p. i, col. 4. 




Fig. 99. — Effects of slope exposure on forest distribution, western Montana, looking east from Mt. 
Belmont; see topographic map below. A and C are cool, moist, forest-clad northern exposures, 
B and D are warm, dry, unforested southern exposures. The trees in the foreground grow on a north- 
eastern exposure. For the position of these slopes on the map see corresponding letters in Fig. 100. 
(Barrel!, U. S. Geol. Surv.) 




Scale of Miles 



K 



2 Kilometers 



Contour interval 50 feet 



Fig. 100. — The positions of the letters A, B, C, D, on the map correspond to the positions of the same 
letters on the photograph. Culture omitted except in case of Marysville. 



ROCKY MOUNTAINS. I 319 

taries intruded by granite and other igneous rocks. After the deforma- 
tion of the rocks of the region erosion swept away great quantities of 
the surface material and reduced the topographic profiles to maturity, 
Fig. 99. 

From the standpoint of forestry this great district in western Montana 
is of special interest because of the strong topographic control of forest 
distribution, not by control of rainfall distribution but by control of the 
water supply through variations in slope exposure. Its special signifi- 
cance may be appreciated by contrast with the physical conditions in 
the Cascades. The western slopes of the Cascades are wet, the eastern 
slopes are dry, a rainfall distribution that is directly dependent upon 
topography and that has a marked effect upon the distribution of 
the forest trees (p. 164). Among the minor ranges of Montana, on the 
other hand, there are no great topographic features to obstruct the 
rainfall and to occasion the climatic contrasts so marked in the Cas- 
cades. Slope exposure is here the factor of primary importance in 
forest distribution. The rather evenly distributed rainfall is more 
quickly evaporated on the sunny southern slopes than on the shady 
northern slopes, hence the latter are moist and forest covered, the 
former dry and almost treeless. Since the daily maximum temperature 
of soil and air is generally attained about two or three o'clock in the 
afternoon, the driest slope is the one facing southwest. Hence eastern 
and northeastern slopes are also forested, while western slopes are forest- 
less. The effect of these conditions is heightened by the action of the 
prevailing southwest winds which not only dry the southwest slopes but 
also sweep them clear of snow in winter. The snows accumulate on the 
northeastern or leeward slopes, where they linger until midsummer and 
supply the ground and the vegetation it supports with the necessary 
moisture. These features are exceptionally well developed about Marys- 
ville and the district therefore merits a somewhat detailed description. 

In the Marysville district the Rockies are developed in the form of a 
broad tract extending westward nearly to the Bitterroot Mountains. 
The eastern portion is a rather flat-topped granite batholith. The 
entire district has the features characteristic of topographic maturity — 
"fairly steep slopes, rounded hill crests, and few cliff exposures. On the 
lower elevations the topography is . . . softened, the view showing 
successive tiers of well-dissected foothills with slopes of 10° to 20°." ^ 
The surface is in general covered with a residual soil so thin on the 
upper slopes as to show a large number of rock outcrops especially on 

I J. Barrell, Geology of the Marysville Mining District, Montana, Prof. Paper U. S. Geol. 
Surv. No. 57, 1907, p. 4. 



320 FOREST PHYSIOGRAPHY 

the more resistant formations. The lower elevations are covered with 
a slightly deeper soil, while the main valley floors are deeply filled 
with alluvium. 

The Marysville region is in the transition belt between the lower, 
drier Great Plains on the east and the higher, abundantly watered and 
forested mountains on the north and west. While the soil covering, 
though thin, is suitable for a forest growth, the rainfall and snowfall 
are so light as to support a forest only in favored situations. Marked 
contrasts in climate occur and are due to marked variations in elevation 
and exposure. The result is a striking contrast in vegetation on dif- 
ferent slopes and at different elevations. Fig. 99. 

"The trees are confined largely to the northern and eastern slopes, since these suffer least 
from the drying action of the summer sun on the thin soil and also in spring hold the snow 
longest around the roots. The prevailing winds are from the southwest, with the result that 
the southwestern slopes are swept more or less bare of snow, which accumulates on the lee- 
ward side of the hills. Here, protected by the evergreen trees, stray banks linger until about 
the first of July. 

"The bottoms of the deeper gorges are especially picturesque, offering the contrast of dark, 
forested southern i or western walls and grassy northern slopes, while cotton woods and willows 
grow in clumps and lines along the courses of the streams. 

"On the northern hill slopes the trees continue down to elevations of about 50°° feet, the 
limit varying considerably with the nature of the soil. Below this level the low hills of the 
northern half of the district are bare of trees and almost without grass, but in the gulches 
which trench them scattered pines have found enough moisture to give them a foothold. On 
the lowest levels the prickly pear and bunch grass hold sway. The most desolate portion of 
the district is north of Little Prickly Pear Creek, for here the sandy, porous nature of the sur- 
face renders it doubly difiBcult for vegetation to maintain a foothold, and large areas are covered 
with nothing but shaly shingle or ancient river cobbles." - 

MOUNTAINS OF NORTH-CENTRAL IDAHO 

The mountain ranges of the northern Rockies that we have ex- 
amined thus far lie chiefly east of the Bitterroot axis. An examination 
of Fig. 86 will show a vast mountain region north of the Snake River 
and west of the Bitterroots, a labyrinth of sharp peaks and ridges 
whose steep slopes descend to deep steep-sided canyons. As a rule the 
mountains rise suddenly from the bordering plains and ultimately to 
sharp ridges that attain 11,000 and even 12,000 feet. 

The origin and nature of a large portion of this wild mountain region 
may be appreciated best from a view that embraces the contrasting fea- 
tures of the plains country formed upon the flat basalt sheets that rim 
about the margins of the mountains and extend far westward into Wash- 
ington, as far as the eastern wall of the Cascades. The summit of Bald 

1 It should be remembered that the southern wall of a valley has the same slope exposure 
as the northern slope of a hill. 

2 Idem, p. 6. 



ROCK-Y MOUNTAINS. 



321 



Mountain near the common border of the two regions (lat. 46° 25') 
affords an extensive view eastward over the level crests and maze 




Fig. 101. — View south across Salmon River Canyon, from 
south slope of Caseknife Mountain, showing plateau char- 
acter of Salmon River Mountains. (Lindgren, U. S. Geol. 
Surv.) 

of ridges and canyons that constitute the prin- 
cipal features of the Clearwater Mountains (lat. 
46°). So thoroughly dissected are these moun- 
tains that little of their original flat outline may 
now be seen. For the first 80 miles eastward 
toward the Bitterroot Valley the lonely trail does 
not disclose a settlement or even a miner's cabin. ^ 
The irregular canyon courses are the chief routes 
for transportation by pack mule. It is the 
worst part of the Kentucky and West Virginia 
"mountains" set upon the western fringe of the 
Rockies. 

Four thousand feet below the level of Bald 
Mountain is a scene of far different quality. The 
lava plain of the Columbia, only gently undulating, 
stretches out apparently without limit westward. 
The undulating Camas and Kamiah prairies are 
checkered with waving wheat fields or wild grass, 
and cultivation and prosperity are brought into 
close contact with mountain wilderness. 

Here we have two regions of great difference 
in relief but also with many features that indi- 

1 W. Lindgren, A Geological Reconnaissance across the Bitter- 
root Range and Clearwater Mountains in Montana and Idaho, 
Prof. Paper U. S. Geol. Surv. No. 27, 1904. 







^•2 



32 2 FOREST PHYSIOGRAPHY 

cate peculiar similarities. The basalt plain is comparatively flat to-day; 
once it was still flatter; as time goes on it will become more and more 
irregular, will become indeed very much like the Clearwater Mountains 
are to-day. The even accordance of hill and ridge top levels in the Clear- 
water Mountains and the manner in which the plane of the ridge tops 
cuts across rock of diverse hardness and structure are clear indications 
that the region was once base-leveled and has since that time been up- 
lifted and maturely dissected so that flat land is nowhere visible. Dis- 
section has progressed so far that the once flat tabular summits have been 
transformed into sharp ridges, but it has not yet progressed far enough for 
the rivers to have begun to form valley flats. The result is a typical hill- 
and- valley country, whose resources of forest and mine are difflcult of ac- 
cess, and where agriculture andrelated industries are practically unknown. 

The sudden descent of the Clearwater Mountains to the level of the 
lava plain is due not to differential erosion but to pronounced crustal 
warping or faulting, for there are no structural features that would 
enable erosion to work out a mountain border of this character. The 
sudden and notable descent from the level of the plateau to the level of 
the plain was brought about probably at the time of uplift, for deep 
canyons were cut following the uplift and before the extrusion of the 
lava (Miocene) that runs up the old valleys now extending westward 
under the lavas. A similar abrupt border characterizes the plateau of 
the Boise Mountains where these descend to the lower valley of the 
Snake River. About the western base of the Clearwater Mountains 
the basalt flooded the foothills to a height of 3000 feet and greatly 
reduced the relief of the region, for the foothills in many cases had 
a sharply accentuated topography. Above the level to which the lava 
rose the courses of the streams draining the Clearwater Mountains 
have been steadily deepening.^ 

Both the Clearwater and the Salmon River mountains are portions 
of a once gently undulating plateau that has been so deeply eroded by 
powerful streams that they stand out with great distinctness. The 
plateau which their crests outline is from 1000 to 3000 feet below the 
summit of the Bitterroot Mountains, causing the latter to appear as a 
boldly raised block. ^ 

Throughout the mountain region of central Idaho the canyons are 
so deep and steep-sided that many of them are quite impassable.^ The 

1 W. Lindgren, A Geological Reconnaissance across the Bitterroot Range and Clearwater 
Mountains in Montana and Idaho, Prof. Paper U. S. Geol. Surv. No. 27, 1904, p. 78. 

2 Idem, p. 13. 

3 G. H. Eldridge, A Geological Reconnaissance across Idaho, i6th Ann. Rept. U. S. Geo!. 
Surv., pt. 2, 1894-95. P- 220. 



rocS:y mountains, i 323 

canyon walls are precipitous, sheer drops of 1000 feet being quite common, 
and the adjacent mountain slopes rise by steep ascents 2000 to 3000 
feet higher. The most rugged canyons are those of the South Fork 
of the Boise River, numerous branches of the Clearwater, and the 
Middle Fork of the Salmon. A stream with typical characteristics is 
the Salmon River, which heads at the foot of the Bitterroot range, 
then flows westward through a wide open valley to a point near 
Shoup, where it enters a profound canyon through which it flows with- 
out interruption for about 250 miles to its junction with the Snake. 
The canyon extends through one of the wildest and least-known parts 
of the state, and is itself so narrow and abrupt and so deep (3000 to 
5000 feet) as to be almost untraversable.^ 

The mountainous country north of the Snake River and west of the 
Bitterroot divide may be divided on the basis of structure into three 
parts : 

(i) A great central granite area 100 miles wide and 300 miles long, 
extending from the Snake River plains northward to an unknown 
distance but at least as far as 45° 30'; it probably ends near the north- 
ern border of the Clearwater drainage." 

As thus outlined it forms one of the largest granite batholiths on the continent. Near the 
lower Salmon River and also near the Seven Devils in the Snake River Valley it is margined by 
sedimentary rocks. A similar contact occurs on the eastern border of the granite, and from the 
nature of the intruded beds it is known that the granite mass is probably of Cretaceous age and 
is an intrusive body similar to the great granitic batholiths of the Sierra Nevada. The granite 
is remarkably uniform in character except in places upon its margin as on the eastern border 
of the Bitterroot Mountains where it has a gneissoid structure owing to metamorphism at 
the time of the formation of the range. ^ 

(2) Partly metamorphosed rocks of sedimentary origin — slates and 
limestones accompanied by schists — occur on the western border of the 
granite area and form the western border of the mountains. 

(3) Partly metamorphosed rocks — quartzites, conglomerates, slates, 
shales, and limestones — occur on the eastern margin of the great granite 
batholith.4 

Two types of mountains have been developed upon these rocks and 
structures: (i) those consisting of masses of rock without any definite 
range trend and developed upon the almost structureless granite of 

1 W. Lindgren, The Gold and Silver Veins of Silver City, De Lamar, and Other Mining Dis- 
tricts of Idaho, 20th Ann. Rept. U. S. Geol. Surv., pt. 3, 1898-99, p. 78. 

2 W. Lindgren, A Geological Reconnaissance across the Bitterroot Range and the Clear- 
water Mountains in Montana and Idaho, Prof. Paper U. S. Geol. Surv. No. 27, 1904, p. 17. 

3 Lindgren and Drake, Silver City FoUo U. S. Geol. Surv. No. 104, 1904, p. i, col. 4. 

* W. Lindgren, The Gold and Silver Veins of Silver City, De Lamar, and Other Mining Dis- 
tricts in Idaho, 20th Ann. Rept. U. S. Geol. Surv., pt. 3, 1898-99, pp. 79, 86-89. 



324 FOREST PHYSIOGRAPHY 

homogeneous texture. The Clearwater Mountains north of the Salmon 
River and the Salmon River Mountains south of the Salmon River are 
the best representatives of this type. The second type of mountain 
occurs in ranges and is the result of erosion of sedimentary^ rock and 
foliated schists, or a rock complex, whose secondary structures on 
erosion give a rough trend to the elevated portions. 

In some of the granites of the western half of Idaho east-northeast- 
trending structures show chiefly in lines of jointing, in the strike of 
foliation planes, or in the trend of the fissures. West of the Sawtooth 
range the divides between the drainage basins are with few exceptions 
due to early structural features — folds, faults, joints — but over most 
of the tract the granite is homogeneous, the structural features are only 
slightly pronounced, the disposition of the topographic elements is a 
response to the disposition of the early drainage systems, and no 
well-defined outlines of a range system can be identified.^ 

The irregular ranges that rise above the general level as in the Sawtooth 
Mountains seem to owe their existence to greater resistance to erosion 
rather than to folding and faulting. A few exceptions to this rule are 
(i) Boise Ridge, which seems to have been partly outlined by orographic 
disturbances, and (2) smaller ranges which have been developed where 
the granite is strongly foliated. v 

The mountains of the range type occur chiefly in the eastern part 
of Idaho near the continental divide in a region of pronounced up- 
lift. They trend in two different directions, east-northeast and west- 
northwest, depending upon the strike of the beds upon which they 
are developed. They are composed of altered or unaltered quartzites, 
schists, and limestones. The Smoky Mountains are an illustration of 
this type; the Bitterroots are a larger and better known unit and receive 
more extended description in the succeeding paragraphs. 

BITTERROOT MOUNTAINS 

From Hamilton or Missoula in the Bitterroot Valley and in the heart 
of the northern Rockies one may look west at the bold front of the 
Bitterroot Mountains. For many miles it maintains a quite remark- 
able regularity of form and straightness of trend. The slope descends at 
angles between 18° and 26°. The rectilinear quality is owing to a fault 
whose locus is the foot of the scarp and whose throw approximates the 
present difference in elevation between range top and valley bottom. 

1 W. Lindgren, The Gold and Silver Veins of Silver City, De Lamar, and Other Mining 
Districts in Idaho, 20th Ann. Kept. U. S. Geol. Surv., pt. 3, 1898-99, p. 77 



ROCKY MOUNTAINS. I 



325 




S > 



326 FOREST PHYSIOGRAPHY 

At least two groups of facts strongly support this explanation, (i) 
Faulting occurred in the region so recently as 1898, when for 1500 feet 
along the base of the mountains a displacement of from i to 2 feet was 
effected and may be observed in favorable localities to-day. (2) AH 
the streams flowing eastward down the regular mountain front have 
remarkably straight courses, and all have steepened gradients in the 
last mile or more before debouching upon the valley flat bordering the 
Bitterroot River. The steepened gradients are an expression of pro- 
gressive faulting which has prevented the attainment of a profile of 
equilibrium, approach to such a profile being counteracted by a repeti- 
tion or continuance of faulting.^ 

The remarkable regularity of the eastern slope of the Bitterroot 
Mountains is the more interesting because of the preservation of the 
fault plane throughout the slope up to the eastern summit, a fact which 
appears to be explained by the flat angle at which the slope was formed, 
the uniform character of the crystalline rock (gneiss and schist) com- 
posing the eastern front of the range, and the original regularity of the 
fault. 

The main divide of the Bitterroots is a succession of sharp craggy 
peaks alternating with deep saddles at the heads of the large canyons 
where glacial cirques have opened up the valley heads. The western 
slope is more rugged than the eastern, although even the latter is almost 
unknown except to prospectors. The immense steep-sided gorges, 
sheer precipices, and extensive rock slides make the western slope en- 
tirely impassable toward the crest. ^ The trails, originally located by 
the Indians, follow the divides or primary ridges as closely as possible, 
tortuous as they are; only grading would make the canyons passable. 

CLIMATIC features; vegetation 

The character of the primeval forest of northern Idaho and north- 
western Montana varies according to latitude, altitude, and conditions 
of exposure. The size of the trees decreases toward the north; on the 
slopes of the Cceur d'Alene Mountains it is not uncommon to find trees 
2 or 3 feet in diameter, while tamarack, spruce, and lodgepole pine along 
the international boundary are seldom more than i foot in diameter. 
The valley terraces along the principal rivers support large groves 
of yellow pine and tamarack, almost without underbrush. The moun- 

1 W. Lindgren, A Geological Reconnaissance across the Bitterroot Range and Clearwater 
Mountains in Montana and Idaho, Prof. Paper U. S. Geo!. Surv. No. 27, 1904, p. 49. 

2 J. B. Leiberg, Bitterroot Forest Reserve, 20th Ann. Rept. U. S. Geol. Surv., pt. 5, 1900, 
P- 319- 



ROCKY MOUNTAINS, I 327 

tain slopes have a denser cover of fir, spruce, and tamarack, which 
with increasing elevation becomes an open growth of spruce, with 
a luxuriant cover of grass. Snow does not persist throughout the year 
upon any of the slopes much exposed to the direct rays of the sun, 
though perennial banks form on the steep northward-facing sides of 
the higher peaks and one or two small glaciers occur in the Cabinet 
range. There is a wet and a dry season, the latter beginning about 
October i, the former about June 15, and the summers are very mild 
and agreeable. The mountainous part of northern Idaho and north- 
western Montana has a thin population engaged in lumbering, agri- 
culture, and mining.^ 

The vegetation of the mountainous area immediately north of the 
Snake River plains consists of forests of fir and pine, above an eleva- 
tion of 5000 feet and gradually increasing in luxuriance northward. 
The southern foothills of the main mountain area below 5000 feet are 
barren. The agricultural population of the Snake River Valley is con- 
centrated chiefly where the tributaries issue from the mountains and 
on the limited flats along the main river, where irrigation is possible. 
Besides these plains settlements are others in the intermontane 
valleys on the Weiser, Payette, and upper Salmon. Scattered mining 
settlements are also found from south of the mountains to Florence, 
and from the Seven Devils to Challis. They are often in places 
very difficult of access and at elevations ranging from 4000 to 8000 
feet. 

In the Bitterroots the soils of the mountain slopes are composed of 
granite debris below and loam above; in the canyon bottoms similar 
conditions obtain, but the top layer is usually heavier; in the subalpine 
meadows the subsoil is a pure granite gravel and the surface layer a 
loam varying from 6 inches to 6 feet in depth.- 

Forests of economic value are found in the Bitterroot Mountains, in 
the upper valleys of the branches of the Bitterroot River, in the can- 
yons of its tributaries farther north, and on the lower slopes of the 
mountains. At greater altitudes and upon the sides and summits of 
the mountain spurs the forests are thin and of little value. Two zones 
of forest distribution may be distinguished, the dividing line lying 
about 5800 feet above sea level. The lower is the yellow-pine zone, 
the upper the alpine-fir zone. The timber of the lower zone consists 

1 F. C. Calkins, A Geological Reconnaissance in Northern Idaho and Northwestern Mon- 
tana, Bull. U. S. Geol. Surv. No. 384, 1909, pp. 20-21. 

2 J. B. Leiberg, Bitterroot Forest Reserve, 19th Ann. Rept. U. S. Geol. Surv., pt. s, 1897-98, 
pp. 262-267. 



328 FOREST PHYSIOGRAPHY 

mainly of red fir and yellow pine in the proportions of 60% and 30%; 
in the subalpine zone nine-tenths of the timber consists of lodgepole 
pine of little commercial value. ^ The former type of growth prevails on 
the lower slopes and in the canyons; the latter occurs on the summits 
and ridges and on the steep upper slopes. 

1 Henry Gannett, 19th Ann. Rept. U. S. Geol. Surv., 1897-98, p. 57. 



CHAPTER XIX 

ROCKY MOUNTAINS. II 

Central Rockies 

Between the northern and southern Rockies is a group of ranges 
whose principal members are the Absaroka, Wind Ri\^er, Gros Ventre, 
Teton, Laramie, and Medicine Bow mountains. Part of them form a 
belt of broken, rugged country with alpine characteristics on the western 
border of Wyoming, such as the Teton and Gros Ventre ranges; another 
part, including the Wind River and Laramie ranges, extends eastward 
and southward, making a great curve through central and southeastern 
Wyoming in continuation of the Colorado Range of central Colorado. 

All these ranges (and many others of lesser extent not described 
here) are sufficiently alike in certain general characteristics and in geo- 
graphic position to form a family of ranges with prominent traits. 
Many of them are anticlinal in structure, the anticlinal uplift being 
directly related to the mountainous relief, so that uplift along axial lines 
is responsible for the trend of the range heights. The asymmetry of the 
folds is another group quality and in the anticlinal ranges always causes 
one mountain flank to be relatively less steep than the other. Erosion 
is of course variable in degree, because the degree of folding and the 
height of the folded strata are not everywhere the same nor are the 
resistances of the different strata uniform. 

It is sometimes ventured that these structures and forms resemble 
those of the long, narrow, Appalachian ridges of Pennsylvania. The 
comparison is not good as regards structure, for the Wyoming ranges 
have a far less regular structure and trend than the Pennsylvania ridges. 
In regard to form the comparison is wholly at fault. No central core 
or axis of crystalline rock is found in the latter case, and no such heights 
are reached. The Pennsylvania mountains are ridges; the Wyoming 
mountains are ranges. In the one case the even sky line is the result 
of base-leveling; base-leveling has not been generally determined in the 
other case and the sky line is serrate, the crests and peaks rugged and 
in some places lofty. Some of the foothill ridges developed upon the 

329 



330 



FOREST PHYSIOGRAPHY 




Fig. 104. — Outline map of the central Rockies, showing location of principal ranges. 

edges of flanking strata are nearly level for miles, have subsequent valleys 
developed upon soft strata alternating with hard, and in general show 
a rough resemblance to Appalachian mountain topography; but on the 
whole there are far more contrasts than resemblances. 



LARAMIE MOUNTAINS 

The great Colorado or so-called Front Range terminates near the Colo- 
rado-Wyoming line and the mountain axis of which it is but a part 
continues northward in a doulile line of uplifts known as the Laramie 
Mountains on the east and the Medicine Bow Mountains on the west. 
The southern end of the Laramie Mountains is near the North Fork 
of the Cache la Poudre River and is surmounted by a confused mass of 
peaks of considerable height. The front range is also elevated north of 
the Laramie River, where it rises in rugged granite hills. But between 
the North Fork of the Cache la Poudre on the south and the Laramie 



ROCKY MOUNTAINS. II 331 

River on the north is an 80-mile division of the front range ^ of the 
Rockies whose topographic features are in strong contrast to the rugged 
groups both north and south. The average elevation of this section is 
only 7800 to 8300 feet and all but one of the few isolated peaks that 
rise above the general level are under 9000 feet above the sea. Sanders 
Peak, 9077 feet, Central Peak, 8744 feet, and Arrow Peak, 8683 feet, are 
the principal eminences. 

The so-called Laramie Mountains are really an elevated plateau some 
1500 feet above the Laramie Plains on the west and somewhat more 
above the Great Plains that lie beyond their eastern foothill ridges. 
The plateau is cut by many canyons and roughened somewhat by nu- 
merous knobs and short ridges, but these features do not wholly obscure 
the expression of the uplifted peneplain (early Tertiary) formed alike 
upon granite and schist. The interstream areas are smooth or gently 
rolling and even the ridges have rounded summits. The latter together 
with the knobs are residual with respect to the peneplain. The rocks 
are deeply decayed and thick residual soil mantles the remnants of the 
ancient surface. 

The main divide of the Laramie Mountains is a distinct ridge of sand- 
stone and limestone bordered on the east by a scarp from 50 to 200 feet 
high; on the west this ridge descends regularly to the Laramie Plains as 
a dip slope. East of the main divide is a broad area of gneiss and schist, 
the core of the anticlinal axis. Farther east are the hogback ridges of 
sandstone and limestone that form the eastern foothills. The Laramie 
Mountains are structurally a great anticline whose summit has been 
worn away. To the fact that it is an asymmetrical anticline is due the 
gentle western and the steep eastern slopes of the mountains. Locally, 
faulting has occurred on the eastern border and heightened these topo- 
graphic contrasts. At other places the contrasts are lessened by an 
extensive overlap of Tertiary deposits which on the east extend far up 
the mountain slopes concealing the underlying harder rocks and afford- 
ing easy ascents to the mountain or plateau summit.- 

There is a noticeable lack of timber over this entire section. Small 
groves of pine, aspen, and other types of tree growth are found in 
sheltered localities, as in the larger basins, but on the whole the timber 
is of little practical importance.^ 

1 The name applied to the easternmost great range of the Rocky Mountain System. In 
Colorado the front range is the Colorado Range; in Wyoming it is the Laramie and other 
mountains; in Montana it is the Lewis Mountains, etc. 

2 Darton, Blackwelder, and Siebenthal, Laramie-Sherman Folio, U. S. Geol. Surv. No. 173, 
1910, pp. I, 2, 13. 

' Arnold Hague, U. S. Geol. Expl. of the 40th Parallel (King Surveys), vol. 2, 1877, pp. 5-7. 



332 FOREST PHYSIOGRAPHY 

WIND RIVER RANGE 

The Wind River Range trends southeast and is one of the eastern 
border ranges of the central Rockies, Fig. 104. It continues toward the 
north in Hne with the Laramie Range, and Hke it is one of the front 
ranges of the system. The general structure of the Wind River Range 
is that of a complex anticlinal whose short and steep dips and corres- 
ponding steep slopes are toward the southwest; the northeast descents 
are less steep. The latter aspect is varied by two parallel mountain 
ridges formed upon hard strata, the intervening soft strata having been 
cut away by strike or subsequent streams. The main summit of the 
mountains consists of a broad plateau-like tract of granite and gneiss 
whose northeastern and southwestern faces are precipitous and deeply 
scored by large canyons.^ 

In the Wind River Range spruce and lir constitute the main tree 
species, with occasional groves of yellow pine and quaking aspen. Below 
the foothill elevations the willow and the quaking aspen grow along 
stream courses; at still lower elevations and in dry interstream situa- 
tions sage-brush and cacti are the characteristic plants, as in the low 
country east of the Wind River Range and north of the Sweetwater 
Plateau. On dry ridges and steep dry bluffs pinon and cedar, or more 
properly, juniper, are found.^ 

BEARTOOTH AND NEIGHBORING PLATEAUS 

The Yellowstone River after leaving Yellowstone Park makes a great 
northerly bend between w^hich and the Bighorn basin are the Bear- 
tooth Mountains or Plateaus, East and West Boulder plateaus. Lake 
Plateau, etc., and the northern end of the Absaroka Mountains. In 
fact the three last-named tracts, together with the Buffalo Plateau and 
other minor subdivisions, constitute the northern part of the Absarokas 
as shown in Fig. 105. They are drained northeasterly by the Stillwater, 
Clarke Fork, and other tributaries of the Yellowstone, through deep 
canyons bordered by wall-like cliffs from 1500 to 3000 feet high. The 
region is everywhere extremely rough, and scored by deep, narrow, 
rocky canyons between which are (i) narrow ridges often only a few 
feet wide at the top or (2) broad, massive, rolling, bowlder-strewn, 
plateau-like surfaces like the East and West Boulder plateaus. The 

1 Orestes St. John, U. S. Geol. and Geog. Surv. of the Terr. (Hayden Surveys), 1877, 
pp. 228 et seq. 

2 F. M Endlich, U. S. Geol. and Geog. Surv. of the Terr. (Hayden Surveys), 1877, 
pp. 59-60. 



ROCKY MOUNTAINS. II 



333 




Contour interval 200 feet 



Fig. 105. — Topography of East and West Boulder plateaus, northern end of the Absaroka Range, south- 
western Montana. (Part of Livingston quadrangle, U. S. Geol. Surv.) 



334 FOREST PHYSIOGRAPHY 

average elevation is about 8000 feet; the canyon floors are at 4000 and 
the highest peaks at 11,000 feet. 

The Beartooth Plateau, the main mass of high, rolling, inter-canyon 
country, and the associated ranges or plateaus, lie east of the Stillwater 
and at higher levels, 9000 feet, with peaks reaching to 13,000 feet. The 
canyons are here also steep and deep and end in rock-bound glacial 
cirques whose development about the bases of the mountains has 
sharpened the latter from a more rounded form into peaks and pinnacles 
of the matterhorn type that give an aspect of profound relief. The 
main plateau is pitted with glacial depressions, many of which have 
lakes and marshes bordered by alpine meadows. On the western border 
of Beartooth Plateau is the deep canyon of the Stillwater; on the east the 
plateau ends in a great frontal scarp in some places more than 3000 feet 
high. The steepness of most of the forms is owing to the late uplift 
of the region, the profound dissection by both water and ice, and the 
resistant gneisses and other crystallines out of which they have been 
carved. Some of the canyons are mere rifts between almost perpendic- 
ular w^alls; most of the headwater cirques are sheer cliffs; the peaks are 
generally glaciated and their bases carved by ice and water to such an 
extent as to give them great steepness and sharpness of form both in 
general outline and in detail. 

The plateaus and canyons in the entire region as well as in the Absa- 
roka and Gallatin ranges on the west were entirely covered with snow 
and ice during the glacial period; in addition all were profoundly dis- 
sected even before glaciation set in. Each range therefore repeats the 
general features of its neighbor. All are characterized by broader or 
narrower plateau-like tracts between deep canyons; all have some sur- 
mounting peaks; all have glacial lakes (i) on the cirque floors, (2) on 
the plateau summits, and (3) in the valleys, where either unequal cutting 
or morainic damming originated basins of variable size. 

The forests of the region are almost wholly coniferous. Limber pine 
grows in belts from 5500 to 6000 feet high; lodgepole pine grows at 
elevations ranging from 5000 to 8000 feet; red fir is most commonly found 
on dry rocky slopes; and Engelmann spruce grows along the canyon 
bottoms or along seepage lines. Above the lodgepole pine forest are 
subalpine fir, white-bark pine, and Engelmann spruce. Timber line is 
at 9300 feet on northern and western slopes and at 9800 feet on south- 
ern slopes. Toward the east it rises and on the eastern edge of the Bear- 
tooth Plateau is at 11,000 feet. At the upper limit of tree growth the 
spruce and the white-bark pine decrease in height and become mere 
crooked shrubs. Grass grows in the alpine zone in such abundance as 



ROCKY MOUNTAINS. II 335 

to form a thick turf capable of storing water and adding to the effect of 
lakes and tarns in preventing too rapid run-off and gullying. Overgrazing 
immediately starts gully erosion and results in effects as important as the 
overcutting of the forests at lower elevations.^ 

ABSAROKA RANGE 

The Absaroka Range extends in a north-south direction for over 80 
miles, with an average width of nearly 50 miles, Fig. 105. The southern 
end of the range is closely related to the Wind River Plateau and the 
Owl Mountains and is made up of enormous volcanic flows. The Absa- 
roka mountains are to be considered as a broad deeply-eroded plateau 
rather than a sharply outlined range, Fig. 105. Profound erosion has 
carved the former more extensive summit into a topographic complex of 
rugged peaks and jagged pinnacled mountains bordered by bold escarp- 
ments which rise to heights of hundreds and even thousands of feet 
above the surrounding country. The walls encircling the mountain 
groups are usually abrupt and owe much of their steepness to ice 
action. 

After the volcanic materials of which the Absaroka mountains are 
largely composed had accumulated the streams cut the range into 
isolated mountains and broadly-spreading spurs and its deep broad 
valleys were occupied by glaciers. All the upper valleys on the eastern 
slopes of the mountains have been sculptured by ice action, and lateral 
and terminal moraines are abundant. In addition, many narrow can- 
yons are broadly benched a thousand feet or more above the valley 
floors, and rounded and polished forms are characteristic features of the 
scenery wherever gneisses and granites occur. 

The chief effects of glaciation are, however, to be found upon the west- 
ern slopes of the Absaroka Range, where a heavy ice cap developed, — 
one of the largest local glacial centers developed in the Rocky Mountains 
south of the great continental ice sheet. This local ice cap was confluent 
with that in the Yellowstone National Park, where a broad area of elevated 
country supplied favorable conditions for extensive glacial accumulations 
which fed marginal glaciers deploying down the valleys.- In the deep 
basins of some of the higher valleys facing northeast, a few snow-fiields 
are still to be found and even small glaciers. The glaciers lie in broad, 

1 J. B. Leiberg, Forest Conditions in the Absaroka Division of the Yellowstone Forest 
Reserve, Montana, and the Livingston and Big Timber. Quadrangles, Prof. Paper U. S. Geol. 
Surv. No. 29, 1904, pp. 10-21. 

2 W. H. Weed, The Glaciation of the Yellowstone Valley North of the Park, Bull. U. S. 
Geol. Surv. No. 104, 1893, p. 13. 



336 



FOREST PHYSIOGRAPHY 




> 

^ m 

P^ _• 
o 

1o 

o 
'S in 



ROCKY MOUNTAINS. II 337 

rock-bound amphitheaters in great measure protected from the direct 
rays of the sun between high walls, and in localities where the prevailing 
southwest winds deliver vast quantities of snow during the winter 
season.^ 

The greater part of the Absaroka Range in the Yellowstone National 
Forest is clothed with coniferous forests broken by open glades. The 
isolated peaks and irregular crests of the main ridges are above timber 
line, and bear only scattered and stunted growths of weather-beaten trees. 
The western side of the range has a more continuous forest cover than 
the eastern. Lodgepole pine is the prevailing tree, limber pine is found 
at higher altitudes, and balsam and spruce are scattered widely though 
they nowhere attain great height or size. The most stately and vigorous 
tree of the Absarokas is the Douglas spruce, but it has a scattered 
growth. None of the timber of the Absaroka region is of superior 
quality, though sufficient for local requirements may be obtained by 
judicious use of the forest.^ 

MEDICINE BOW RANGE 

This range is about loo miles long and diverges slightly with respect 
to the front range. Included between it and the front range is a 
high intermont basin, so-called Laramie Plains. Its broadest part, in 
the region of Medicine Peak, is from 30 to 35 miles across, but the 
southern end is only 10 or 12 miles wide. The highest peaks named 
from the southern end northward are Mount Richthofen, 13,000 feet; 
Clark's Peak, 13,100 feet; Medicine Peak, 12,200 feet; and Elk Moun- 
tain, 11,500 feet. North of the 41st parallel the range becomes double 
crested in response to the double anticlinal structure, but tow^ard the 
south its unity is preserved. Between the double crests of the northern 
section is a high, gently undulating, intermont plateau 10,000 feet above 
the sea, whose surface is covered with timber and dotted with lakes. 
All the higher portions of the range have been glaciated, and some of 
the glacially carved amphitheaters are very striking, with steep walls 
1500 feet high cut in extremely hard quartzite. 

The greater part of the range is covered with coniferous forest which is 
in places quite dense. Douglas spruce, Engelmann spruce, and yellow 
pine are the chief species. The cold timber line is about 11,000 feet 
above sea level. ^ 

1 Arnold Hague, Absaroka Folio U. S. Geol. Surv. No. 52, 1890, p. 6, col. 3. 

2 Idem. 

^ Arnold Hague, U. S. Geol. Expl. of the 4otli Par. (King Surveys), vol. 2, 1877, pp. 94-97. 



338 



FOREST PHYSIOGRAPHY 



BASIN PLAINS OF SOUTHERN WYOMING AND MINOR RANGES ON THEM 

An accurate relief map of the Rocky Mountains represents a broad 
and flat tableland between the Laramie Mountains and the ranges west 
of the Green River. Through the eastern portion of this tract runs the 
Medicine Bow Range and through the central portion run the Leucite 
Hills, etc., so that the tract is partially divided into three sections. 
The portion east of Medicine Bow Range is called the Laramie Plains; 




Fig. 107. — Laramie Plains, looking southwest from near Mandel, Wyo. (U. S. Geol. Surv.) 

the central section is known as the Red Desert, etc.; and the western- 
most section is known as the Green River Basin. These three main 
divisions are, however, continuous about the northern end of their moun- 
tainous boundaries. 

The Laramie Plains are 7000 feet above sea level, have a relatively 
smooth and gently undulating surface. Fig. 107, with gentle slopes and 
rounded outlines, so that they appear practically level over broad ex- 
panses except where a few bench-like ridges or very low buttes of cir- 
cumdenudation occur. Shallow lakes, none more than a few square 
miles in extent, are scattered over the surface of the plain, whose 



ROCKY MOUNTAINS. II 339 

waters range from fresh to brackish or strongly alkaline; some of them 
disappear during the dry season and leave saline incrustations. The 
whole tract is a great natural pasture; trees grow only along the broad 
stream valleys.^ 

The Laramie Plains apparently owe their flatness to the general 
horizontal attitude of the underlying strata (Cretaceous). The highest 
observed dips in the central portions of the basin are 12°, the average 5° 
to 8°. On the borders of the basin the dips increase somewhat and the 
eroded strata present steep bluffs toward the older rocks that form the 
cores of the bordering ranges. One of the most typical portions of 
the high intermont plains of southern Wyoming is the central division, 
which extends west of Rawlings. There are but few exposures of the 
flat-lying beds, and these occur only in escarpments a few feet high. 
The barren surface is but slightly dissected by the dry, shallow water- 
courses that traverse it. It is a flat, monotonous region as far as the 
Leucite Hills and is broken only at long intervals (i) by hills of erup- 
tive material, or (2) by lines of moving sand dunes and drifts, as west of 
the Red Desert and north of the Leucite Hills, or (3) by local uplifts of 
small extent as at Rawlings. No marked drainage features are found 
in this section, but the section west of the 109th meridian is drained 
by the upper tributaries of the Green and along their courses an im- 
portant amount of dissection has taken place. ^ 

The westernmost section of the Wyoming Plateau is also under- 
laid by nearly horizontal strata (Tertiary and Cretaceous) . The general 
nature of the relief is similar in most respects to that of the eastern 
divisions. The central depression of the tract is occupied by the valley 
of Green River, which on the north flows through the basin in a wide 
alluvial bottom; farther south it flows through a 1000-foot canyon cut 
in nearly horizontal strata (Tertiary). It then enters the Uinta range 
at the Flaming Gorge, where it cuts through the hardest quartzite, 
turns out of the mountains, flows eastward, and finally cuts straight 
across the Uintas in a superb 3000-foot quartzite canyon known as the 
canyon or gate of Ladore.^ 

The Green River drains a great basin whose eastern portion is some- 
what diversified by low, strike ridges of irregular outline and whose 
western portion bears ridges of similar structural nature but of more 
regular topographic development, the horizon being always bounded 

1 Arnold Hague, Rocky Mountains, U. S. Geol. Expl. of the 40th Par. (King Surveys), vol. 2, 

1877, PP- 73-75- 

2 S. F. Emmons, The Green River Basin, U. S. Geol. Expl. of the 40th Par. (King Surveys), 
vol. 2, 1877, p. 164; and Geol. Map by Peale, St. John, and Endlich, accompanying Report. 

' Idem, pp. 192-193 and 287, with Plate 8. 



340 FOREST PHYSIOGRAPHY 

by an almost perfectly horizontal line.^ The southern portion of the 
region north of the Park Range, known as the Savory Plateau, likewise 
presents a horizontal sky line, but for a different reason. The surface 
strata (Tertiary) are horizontal here and overlie the upturned and 
eroded edges of Cretaceous and older beds and present smooth plain 
surfaces." From these stratigraphic relations it is reasonable to con- 
clude that a mountain-making period at the close of the Cretaceous or 



Fig. io8. — Terrace and escarpment topography of nearly horiEontal beds (Eocene), Green River Basin, 
southwestern Wyoming. (Veatch, U. S. Geol. Surv.) 

in early Tertiary deformed the underlying beds and erosion planed them 
off, some perfectly, others imperfectly, and that upon the subdued, 
partially reduced surface thus developed. Tertiary beds of great 
thickness (up to looo feet) were deposited. Erosion dissected (i) the 
Cretaceous strata that were never buried, causing the development of a 
ridge and valley type of topography, and (2) the Tertiary cover, in some 

1 S. F. Emmons, The Green River Basin, U. S. Geol. Expl. of the 40th Par. (King Sur- 
veys), vol. 2, 1877, p. 192. 

2 Idem, p. 164. 



ROCKY MOUNTAINS. II 



341 



instances, laying bare the Cretaceous beneath, in others exposing only 
Tertiary material in the valley sections. 

Similar relations have been identified in southwestern Wyoming and 
on the southwestern border of the Green River Basin. The basin floor 
is here developed chiefly upon Tertiary strata dipping gently eastward, 
and in general has been eroded so that the strata present their outcrop- 
ping edges as westward-facing escarpments, a typical terrace topog- 
raphy. In places the mantle of nearly horizontal Tertiary deposits 
has been worn away and the underlying older beds with steep inclina- 
tion are now exposed. Since there is considerable difference in the 
exact degree of dissection of the capping strata and of the exposed 
portions of the underlying, deformed rocks, the topography also varies 




Fig. 109. — Hogback topography of inclined beds (pre-Eocene), southwestern Wyoming. The crests of 
the ridges are developed upon sandstone underlain by shale. (Veatch, U. S. Geol. Surv.) 



from place to place. Two main types of topography have been de- 
veloped: (i) flat table-like forms in places with bordering escarpments 
of considerable length between benches that rise in regular succession, 
a topographic type developed upon the uppermost and horizontal beds; 
(2) long ridges, often sharp, separated by equally long valleys, the whole 
in a markedly parallel arrangement and developed upon the steeply in- 
clined older rock composed of alternating hard and soft layers. Hard 



342 FOREST PHYSIOGRAPHY 

sandstones are the ridge makers ; soft shales underUe the valleys and the 
lowlands.^ 

The greater portion of the Green River Basin presents a gravel-strewn 
surface almost everywhere in process of dissection. The gravel cap was 
formed (i) by the weathering in place of the partly consolidated or 
wholly unconsolidated deposits filling the basin, or (2) by detrital accu- 
mulations washed into the basin during an earlier period of aggradation. 
The latter material is abundant about the mountainous border of the 
basin and originated in the form of desert-fan deposits. Its origin may 
be related to the renewed growth of the bordering ranges. Its deposi- 
tion was preceded by a long erosion interval in which a local peneplain 
was formed, a fact which partly explains the extent of the gravel cap. 
It was followed by erosion now in progress.^ 

The Leucite Hills, which partially break the continuity of the plains 
of southern Wyoming, consist of a number of small conical peaks of 
volcanic origin. Some of them are capped by lava flows, others have 
crater-like forms and appear to have been centers of eruption.^ They 
have no great topographic prominence and are of little interest in the 
present connection. 

SIERRA MADRE RANGE 

Continuing with the mountain ranges of the central Rockies it should 
be noted that in south-central Wyoming (Encampment District, south of 
Rawlings and west of the Medicine Bow Range) the mountain topog- 
raphy is on a whole of a subdued type. Steep slopes are confined to 
the middle courses of a few of the main streams and to a few basins 
or amphitheaters near the main divide formerly occupied by glaciers. 
The Sierra Madre mountains here form the main or continental divide. 
Their summits are generally broad and form a flat surface whose eleva- 
tion ranges from 9200 feet in the lowest pass to 11,000 feet on the high- 
est summit. The steep headwater declivities on opposite sides of the 
divide are often a mile or more apart, and the soft, broader-spaced con- 
tours of the mountain summits are frequently continued out upon the 
marginal spurs for several miles. The high portion of the range. Fig. no, 
thus appears as an elevated plateau submaturely dissected by existing 
streams. The topography is subdued rather than rugged, and wagon 

1 A. C. Veatch, Geography and Geology of a Portion of Southwestern Wyoming, Prof. Paper 
U. S. Geol. Surv. No. 56, 1907, pp. 34-35, and Plate i. 

- J. L. Rich, The Physiography of the Bishop Conglomerate, Southwestern Wyoming, 
Jour. Geol., vol. 18, 1910, pp. 601-632. 

3 S. F. Emmons, U. S. Geol. Expl. of the 40th Par. (King Surveys), vol. 2, 1877, p. 236. 



ROCKY MOUNTAINS. II 



343 



roads have been constructed on almost every portion of the area with- 
out that excessive expense that is usually required in opening trans- 
portation routes in mountainous regions.^ 

The general structure of the Sierra Madre Mountains is a low arch or anticline the axis of 
which is parallel with the mountain crest. This arch was gradually uplifted and eroded and 
the Mesozoic rocks removed from the axial portion, revealing older pre-Cambrian rock which 
forms the main mass of the mountains. The Mesozoic formations outcrop on the foothills on 
either side and dip away beneath the surrounding plains. 




Fig. no. — Mature profiles, long gentle spurs, and rounded summits of the mountains of the Encampment 
district, south-central Wyoming. (Encampment Special quadrangle, U. S. Geol. Surv.) 



TETON RANGE 

The Teton Range extends almost due south from the southwestern 
corner of Yellowstone Park and just east of the Idaho- Wyoming line. 
It is about 40 miles long and from 10 to 15 miles wide, with a central 
cluster of exceptionally high peaks, the highest of which, Mount Hayden 
and Grand Teton, attain elevations of 13,700 feet and 13,800 feet re- 
spectively. The only practicable pass is Teton Pass at 8400 feet. 
There are still in existence several small glaciers occupying cirques high 

I A. C. Spenser, The Copper Deposits of the Encampment District, Wyoming, Prof. Paper 
U. S. Geol. Surv. No. 26, 1904, pp. 12-15. 



344 FOREST PHYSIOGRAPHY 

up in the range. The Tetons consist of a great longitudinal axis of 
uplift and folding; the steep and short descent is on the east, the longer 
and gentler is on the west. The steep eastern front is cut into a number 
of great buttress-like spurs faced by bold precipitous cliffs. On the west 
are a number of long narrow canyons separated by broad westward- 
descending slopes. These features are very uniformly developed along 
the entire eastern and western mountain fronts and are the most im- 
portant in the range. The main mountain forms have a very intimate 
relation to a single great anticlinal uplift greatly eroded, exposing a 
central core or nucleus of crystalline rock, chiefly gneiss and granite, the 
latter forming the sharp peaks and aiguilles as well as the highest peaks 
as in Mount Hay den; the gneiss tends to erode into the form of sharp 
ridges. The crest of the range does not everywhere follow the granite 
however. At the south it is developed chiefly upon sedimentary rocks 
that have not yet been stripped from the crystalline foundation.^ 

In general the climatic conditions in the Tetons favor forest growth, 
yet but little forest exists owing altogether to the repeated and destruc- 
tive fires which have swept over the tract. The lodgepole pine has been 
temporarily driven out in many places and former timbered areas have 
become grass-covered parks or aspen groves. Besides lodgepole pine 
and aspen the principal species are Engelmann spruce and red fir, the 
former in damp, the latter in dry situations.- Timber hne is at 10,000 
feet in this locality, and as the average altitude of the range is about 
12,000 feet, large portions of the Tetons rise well above the upper limit 
of the forest. 

GROS VENTRE RANGE 

The Gros Ventre Range consists of two parallel mountain folds or 
anticlines about 5 miles apart, the axes trending southeast. Erosion 
has unroofed both anticlines and given them corresponding topo- 
graphic features. Had the anticlines been symmetric, long, gentle, dip 
slopes would, in the present state of erosion, be found upon the outer 
flanks of the ridges, and steep, short slopes would be found cutting 
across the inner edges of the strata. The folds are, however, not sym- 
metric, for the axes lie near the southwestern margins, hence the south- 
western slopes are steep, the northeastern slopes relatively gentle and 
uniform in character. The contrast is identical in general kind, though 

1 Orestes St. John, U. S. Geol. and Geog. Surv. of the Terr. (Hayden Surveys), 1877, 
pp. 411-416. 

2 T. S. Brandegee, Teton Forest Reserve, 19th Ann. Rept. U. S. Geol. Surv., pt, 5, 1897-98 
pp. 195-107. 



ROCKY MOUNTAINS. II 345 

somewhat dissimilar in detail to that afforded by the eastern steep and 
western less steep slopes of the Tetons. As in the latter case also, 
erosion has denuded the sedimentary cover and exposed portions of the 
underlying crystallines. These do not, however, form any notable por- 
tion of the mountain crest, for denudation is here far less advanced and 
the mountain summits are still largely developed upon sedimentary 
rock.^ 

Extra-Marginal Ranges 

On the eastern and the western borders of the central Rockies are two 
mountain ranges which stand out prominently at a little distance for- 
ward from the main mountain front. The eastern range is the Bighorn 
Mountains; the western range is the Uinta Mountains. Although they 
are here classified as a portion of the central section of the Rockies they 
should be regarded as having no very close geologic or geographic afi&n- 
ities with the Wyoming ranges described above. 

UINTA mountains 

The Uinta range is peculiar in trending in an east-west direction in a 
mountain region where the prevailing trends are north-south. It is not 
altogether unique in this respect, however, for the Owl Creek range is a 
fold having a similar trend, and others in Wyoming and elsewhere hav- 
ing the same trend have been discovered.- 

The Uintas form a rather flat, elliptical dome or elongated arch 150 
miles long from east to west and with an average width of 20 to 25 
miles. The interior of this elongated dome is a deeply dissected, plateau- 
like region, in general about 10,000 feet high, from which rise narrow 
ridges and peaks 12,000 to 13,000 feet high developed upon horizontally 
bedded quartzites.^ 

The strata of the interior plateau nowhere depart more than 5° or 6° 
from a horizontal position except in a small number of local instances. 
On the margins of the mountain belt the beds dip more steeply, in some 
cases over 45° and in extreme instances nearly 90°. The marginal 
zones of highly inclined strata are also affected by minor faults and folds, 
the principal displacement being along the northern side of the arch, 
Fig. 1 11.^ 

1 Orestes St. John, U. S. Geol. and Geog. Surv. of the Terr. (Hayden Surveys), 1877, 
pp. 208 et seq. 

2 N. H. Darton, Senate Document No. 2ig, 1906. 

' S. F. Emmons, Uinta Mountains, Bull. Geol. Soc. Am., vol. 18, 1907, pp. 287-302. 
* W. W. Atwood, Glaciation of the Uinta and Wasatch Mountains, Prof. Paper U. S. 
Geol. Surv. No. 61, 1909, p. 9. See also J. W. Powell, Geology of the Uinta Mountains, 1876. 



346 



FOREST PHYSIOGRAPHY 



The physiography of the Uinta Mountains is closely related to the 
geologic structure. The broad open valleys of gentle contour depend 
upon sculpturing of soft horizontal strata beneath a capping of harder 
beds. The steeply inclined strata on the flanks of the range have been 
eroded to the point where they stand out as a series of hogback ridges 
separated by parallel trough-like valleys. The streams run in a series 
of rapidly deepening canyons with nearly vertical walls 3000 to 4000 
feet high, and are deepest where they cross the hogback ridges on the 



In the background, the Utnta 
Jold is supposed to have re 
7nained uneroded, while 
the foreground shoais 
the iUinta Mount 
1 ains as they exist 




Fig 153 
Fig. III. — Stereogram and cross-section of the Uinta Mountains arch. (Dryer, adapted from Powell.) 

margins of the anticline. The axis of the Uinta uplift is near the 
northern margin and the canyons of the northern slope are therefore 
shorter than those of the southern slope. The inter-canyon spurs are 
broad and flat and are overlapped by gently sloping Tertiary beds in 
places up to elevations of 10,000 feet. 

The Green River enters the northern flank of the Uinta Mountains 
at the Flaming Gorge, then swings out again, only to return and cross 
the main axis of the range at the eastern end through the Ladore Gate 
or Canyon. Powell described the Green River as an excellent illustra- 
tion of an antecedent stream that had maintained its course across 
the Uinta Mountains during the period of their uphft.^ The later 
studies of Emmons show that Powell's hypothesis must be modified, 
for it involves physical impossibilities. 



I J. W. Powell, Geology of the Uinta Mountains, 1876. 



ROCKY MOUNTAINS. II 347 

The upturned and truncated edges of the various formations of the Uinta arch are partly 
covered by overlapping Tertiary beds in a nearly horizontal position. These beds reach alti- 
tudes of 9000 to 10.000 feet at various points on either flank of the higher western portion of 
the range. The Green River Canyon, at the Flaming Gorge, has an elevation in the eastern 
portion of the range of 7500 to 9000 feet. From these conditions it seems clear that (i) the 
mountain-making movements which gave rise to the Uintas were accomplished principally at 
the close of the Cretaceous, though a small subsequent movement is allowable on strati- 
graphic grounds (each of the three series of Tertiary beds is marked by an erosion interval 
between successive beds and by a slight upturning on the flanks of the Uinta Mountains); 
(2) the Green River had its course directed as a consequent stream upon the surface of the 
overlying Tertiary deposits; (3) the dissection of the Tertiary beds allowed the river to be- 
come superposed upon the buried portion of the Uinta arch; (4) further erosion both within 
and on the borders of the range has intensified the topographic expression of the Uinta arch 
and to some extent obscured the origin of the course of the Green River.i 

FORMS DUE TO GLACIATION ^ 

In addition to the influence of alternating hard and soft beds on the 
valley outlines, glaciation has operated to widen and deepen the canyons 
and in many cases to give them characteristic U-shaped profiles. The 
floors of the basins in the western part of the range are about 9000 feet 
in elevation and every large canyon that heads near this part of the 
crest has been glaciated. The glaciers in the central portion of the range 
were 20 to 27 miles long; elsewhere they were but 4 or 5 miles long. 
The ice slopes about Bald Mountain and Reed's Peak near the western 
end of the range coalesced to form a great ice cap, Fig. 112. The greater 
portion of the divide was, however, not covered by ice and the loftier 
peaks rose above the snow-fields. The basins at the heads of the can- 
yons on the northern slope vary in area from i to 1 2 square miles, while 
many of those on the southern slope are 20 to 30 square miles in extent, 
a difference which is due to the fact that the southward-flowing streams 
have developed valleys in the plateau-like summit where the beds are 
nearly horizontal and where the conditions are therefore most favorable 
for glacial plucking and sapping and for the development of broad flat- 
bottomed cirques. The northward-flowing glaciers worked upon steeply 
inclined strata and were resisted by every hard stratum in the section 
instead of a single hard stratum; hence they were but little assisted by 
sapping, for the soft beds whose removal gave rise to the sapping of the 
harder beds above them soon dipped down beneath the plane of effective 
action. The result was not only a greater amount of work to be per- 
formed by the northward-flowing streams but also a restriction of the 
fields of nourishment which correspondingly decreased the intensity of 
glaciation. 

1 S. F. Emmons, Science, n. s., vol. 6, 1897, p. 131 et al. 

2 W. W. Atwood, Glaciation of the Uinta and Wasatch Mountains, Prof. Paper U. S. Geol. 
Surv. No. 61, 1910. 



348 



FOREST PHYSIOGRAPHY 




ROCKY MOUNTAINS. II 349 

FOREST GROWTH 

In the higher portions of the range the forest growth is extremely 
scanty, but in the lower valley basins there is a heavy growth of co- 
niferous forest. The upper limit of forest growth is about ii,ooo feet, 
the lower limit on the southern slopes is beyond the base of the range 
in the Uinta Valley and is less than 7000 feet, while on the northern 
slopes it is 9000 feet owing to differences of relief and to corresponding 
differences of exposure. The prevailing species are white pine, yellow 
pine, Engelmann spruce and Douglas spruce, besides species of lesser 
importance. 

"The view from one of the mountain lalces, with its deep-green water and fringe of meadow- 
land, set in the somber frame of pine forests, the whole enclosed by high walls of reddish- 
purple rock, whose horizontal bedding gives almost the appearance of a pile of cyclopean 
masonry, forms a picture of rare beauty." i 

BIGHORN MOUNTAINS 

The Bighorn Mountains rise from 4000 to 5000 feet above the Great 
Plains to from 10,000 to 13,000 feet absolute altitudes. The range 
trends north-northwest in its northern portion, due north and south 



Fig. 113. — East-west section across highest part of Bighorn Mountains, showing extent of erosion and 
the contrast in dip on the two slopes of the range. 

in its central portion, and east and west where it joins the main Rocky 
Mountain System whose border ranges are known here as the Bridget 
Range and the Owl Creek Mountains.^ It is in effect an extension or 
prodigious spur of the Rockies jutting far out beyond their border. 

The Bighorn Mountains are a great anticline lifted many thousands 
of feet and composed of a thick series of sedimentary rocks (Paleozoic 
and Mesozoic) and a central core of granite and schist (pre-Cambrian).^ 
The sedimentary rocks arch over the northern and southern portions 
of the uplift, and give rise to elevated plateaus about 9000 feet high 
at the north and 8000 feet high at the south. On the divides these 
plateaus often present broad tabular surfaces though they are trenched 
by numerous large canyons. The central plateau terminates in high 
cliffs at certain places in the border region, but in others and especially 

1 S. F. Emmons, Geol. Expl. of the 40th Par. (King Surveys), vol. 2, 1877, pp. i94-ig5. 

2 N. H. Darton, Geology of the Bighorn Mountains, Prof. Paper U. S. Geo!. Surv. No. 51, 
1906, pp. lO-II. 

5 Darton and Salisbury, Cloud Peak-Fort McKinney Foho U. S. Geol. Surv. No. 142, 1906, 
p. I, cols. 2, 3. 



35° 



FOREST PHYSIOGRAPHY 




ROCKY MOUNTAINS. II 35 1 

along the eastern side of the mountains it is flanked by a distinct ridge 
of limestone that rises slightly above an inner valley and slopes steeply 
toward the plains. These plateaus are covered by forests with many 
park-like openings and are extensively used as grazing grounds for cattle 
and sheep during the short summer season. 

The subordinate topographic features of the Bighorns depend upon 
local flexures on the flanks of the main uplift and a number of faults, 
the latter being especially marked northwest of Buffalo and on the 
eastern border of the range, where one of the faults has a throw 
of about 9000 feet. The effect of the sharper flexing and of the pro- 
nounced faulting has been to increase the development of precipitous 
slopes, and to cause a greater development of hogback topography 
especially on the eastern side. The hogback ridges rise from 100 to 
200 feet above the adjoining valleys, and are due to the outcrop of sand- 
stone of moderate hardness, while the valleys follow the outcrop of the 
"Red Beds" composed largely of soft shales. 

The general configuration of the central cluster of high mountains 
in the Bighorns is very rugged and presents some of the boldest alpine 
scenery in the United States. There are many precipices over 1000 
feet high, particularly in the glacial cirques along the higher summits. 
Some of the cirques still hold glaciers; one on the eastern side of Cloud 
Peak is nearly one-half mile long. Extensive snowbanks remain the 
entire summer in many higher portions of the range.^ 



GLACIAL FORMS 

At the tiriie of maximum glaciation in the last glacial epoch the snow 
and ice accumulations of the Bighorns were two or three times as 
extensive as those of Switzerland to-day and the largest glacier was 
considerably larger than the largest existing Swiss glacier.^ For thirty 
miles the crest of the range has been glaciated and signs of glaciation 
are everywhere abundant. The topographic and climatic conditions 
governing the distribution and growth of former glaciers were unusually 
favorable. Glaciers started from approximately one hundred soiurces, 
but in descending they combined in many cases, so that the number 
of separate glaciers or glacier systems was but nineteen. A specific 
instance is the Pear Rock Glacier, which started from not less than 
twenty sources. 

1 Darton and Salisbury, Cloud Peak-Fort McKinney Folio U. S. Geol. Surv. No. 142, 
3906, p. I. 

' Idem, p. 9, col. 4. 





Fig. ij$. — Wall at head of cirque, upper end of a tributary of West Tensleep Creek, Bighorn Mountains. 
A. View from above rim, showing old rounded surface. B. View from below rim, showing granite 
walls nearly looo feet high. (Blackwelder, U. S. Geol. Surv.) 
352 



ROCKY MOUNTAINS. II 



353 



During both the advance and the retreat of the ice the number of 
separate glaciers was greater than during the time of maximum glacia- 
tion, for the ice was melted out of the lower glacial troughs, while it 
still lingered in the separate tributary valleys. The glaciers on the 




^/7,Jm°oo') 



Fig. IK: 



- Glacier systems of the Bighorns at the time of their maximum development, 
welder, U. S. Geol. Surv.) 



(After Black - 



west side covered almost twice as great an area as those on the east and 
they were also somewhat longer, a difference due to the heavier precipi- 
tation on the west side (prevailing westerly winds) and the wider catch- 
ment basins. The surviving glaciers are now found wholly on the east 
side, a condition probably due to the better protection of the cirques 



354 FOREST PHYSIOGRAPHY 

on that side from the sun and in part to the westerly winds which 
drift snow over the crest of the range and into the cirques and alcoves 
on the lower side. The lower limits of the glaciers were from 6500 feet 
to 10,500 feet, the necessary elevation for the generation of glaciers in 
the Bighorn Mountains during the last glacial epoch ranging from 9500 
to 11,500 feet.^ 

Glacial cirques and hanging valleys are of frequent occurrence, though 
aretes and needles are absent because glacial sapping did not continue 
long enough to allow the meeting of glaciers on the divides.- The 
cirque walls have not been notably denuded in postglacial time be- 
cause of the compact and relatively structureless granite in which they 
were carved and in part because of the recency of formation. The 
cirques have been formed on a huge scale, for the original valleys were 
often far apart and neighboring cirques were thus developed without 
mutual interference on the lateral divides.^ 

Below the cirques are steep valleys whose gradients range from 600 
to 800 feet per mile. Where the valleys cross the great central granite 
plateau they are shallower and more open; but where they cross the 
sedimentary rim they become narrow gorges. Some of the longest 
glaciers entered these gorge-like marginal valleys, but none of them 
reached out upon the plains. Among the most important features of 
the present drainage are the large numbers of lakes due to glacial over- 
deepening or to the presence of morainic dams. Some of the terminal 
moraines of the Bighorns are of great size, the undulations of their 
surface reaching as high a value as 800 feet. The terminal moraine 
of North Fork is 300 feet above the level of the valley floor and its 
topography is very irregular.* 



Nearly all the trees of the Bighorn National Forest (which includes 
most of the forested area of the mountains) are lodgepole pine {Pinus 
murrayana, locally called white pine), yellow pine, and jack pine. 
Another species is limber pine of scattered growth. Engelmann spruce 
occurs in some of the moister areas along the mountain slopes and the 
higher portions of some of the canyons. The dry or lower timber line 

1 Darton and Salisbury, Cloud Peak-Fort McKinney Folio U. S. Geol. Surv. No. 142, 
1906, p. 10, col. I. 

2 F. E. Matthes, Glacial Sculpture of the Bighorn Mountains, Wyoming, 21st Ann. Rept. 
U. S. Geol. Surv., pt. 2, 1899-igoo, p. 175. 

' Idem, p. 176. 

* Darton and Salisbury, Cloud Peak-Fort McKinney Folio U. S. Geol. Surv. No. 142, 
1906, p. II, col. 3. 



ROCKY MOUNTAINS. II 355 

occurs at 6000 feet, and the cold timber line at 10,000 feet, so that the 
upper portions of the range do not generally support a timber covering 
of any importance, but on the whole expose "bare rock-strewn summits. 
The wood of the white pine, the predominating species, is coarse-grained, 
knotty, and small. The lumber warps and cracks considerably, and it 
is therefore not regarded as valuable.^ 

• For detailed distribution of the timber of the Bighorns, etc., see 19th Ann. Rept. U. S. 
Geol. Surv., pt. 5. 



CHAPTER XX 

ROCKY MOUNTAINS. Ill 

Southern Rockies 

In contrast to the irregularly arranged mountains of the Central 
Rockies with variable trend, numerous offsets, and plain and plateau 
interruptions are the northward-trending, somewhat regular, and con- 
tinuous mountain ranges that constitute the southern Rockies. There 




Fig. 117. — Location map of the southern Rockies. 



ROCKY MOUNTAINS. Ill 



357 



appears to be a rather well-marked and consistently developed mountain 
plan in the eastern and central ranges of the district; the western- 
most ranges are of more diverse structure, topographic texture and 
origin, and occur in groups of longer and shorter lengths arranged on 
the whole with less regularity. 

Fig. 117 represents the locations of the main topographic features of 
the region, which fall readily into five categories: 

(i) The eastern foothills, of varied origin and commonly exhibiting the 
hogback type of topography. 

(2) The Colorado or Front Range and the Wet Mountains, consisting 
in a broad way of a great anticlinal from whose central granite axis the 
flanking sedimentary beds dip east and west. 

(3) The Park, Sawatch (Saguache of some maps), and Sangre de 
Cristo ranges, all of which lie nearly on the same meridian, trend north- 
ward, have roughly equivalent structures and topographic forms, and 
are parallel to the Colorado Range, from which they are separated by 

(4) a chain of "Parks," North, Middle, South, and Huerfano, four 
intermont basins of exceptional character, primarily of structural and 
secondarily of alluvial origin (San Luis Park, the largest of all the inter- 
mont parks of Colorado, lies between the Sangre de Cristo range and the 
southern continuation of the Sawatch Mountains — the Conejos, etc.). 

(5) Irregular mountain knots or groups of igneous origin which lie 
beyond the Park-Sawatch axes, such as the Elk, La Plata, San Juan, and 
Uncompahgre mountains. 



Hogback . A// /J'/ J' //- ■■ 

'/ / / 





Fig. 118. — Generalized east -west section near Boulder, Colorado, showing the structure and topography 
of the South Boulder Peaks and the hogback ridge o£ Dakota Sandstone. (Fenneman, U. S. Geol. 
Surv. 

EASTERN FOOTHILLS 



HOGBACK TOPOGRAPHY 



The eastern foothills of the southern Rockies are generally formed 
upon a belt of sedimentary beds upturned at steep angles along the 
mountain slopes. The most characteristic feature is the hogback 
ridge, Fig. 118, developed in the form, of long narrow ridges of harder 



358 



FOREST PHYSIOGRAPHY 



beds that stand like a fringing and often a serrated wall at a little 
distance from the base of the mountains. They occupy a belt about 
two miles wide involving portions of all valleys intervening between 

them and the main 
range. The easterly dip 
of the sedimentary beds 
of the foothills is quite 
general, and ordinarily 
varies from 35° to 50°, 
though locally it is from 
80° to 90° 

Besides the general 
flexing of the strata, 
which is due in part at 
least to the uplift of the 
Colorado Range, there 
has been a considerable 
amount of minor crum- 
pling along lines parallel 
with the general trend 
of the range or diverging 
from it to some degree. 
The latter process re- 
sulted in a series of 
secondary folds reflected 
in the topography by 
successive offsets. In 
such localities the ridges 
are arranged en echelon. 
Their general appear- 
ance is shown in Fig. 119, 
which represents a series 
occurring between St. Vrains and Cache la Poudre creeks, north of 
Denver. 

VEGETATION 

The vegetation of the Pueblo region is closely related to climate and 
soil, and in this respect and in its general character it is typical of the 
vegetation of the hogback ridges of Colorado. The uplands above 
6500 feet bear a forest of yellow pine, and straggling pine growths occur 
on sheltered hillsides down to 5300 feet; in the same zone rocky slopes 
are sometimes covered with aspens. Hackberries and other hard- 




FOLDS L.\ I( lli.LKX ALl>N(; ]-|;(_L\T UF COLUlLVDO llA.XUE. 
Sculuot.Uiles 

1 2 i 8 la ^_^ 

QUATERNARY LARAMIE FOX 



Fig. 119. 



Cross folds on eastern border of Colorado Range. 
(U. S. Geol. Surv.) 



ROCKY- MOUNTAINS. Ill 359 

wooded trees grow to moderate size in the moister valleys, while cot- 
tonwoods fringe the lower streams; juniper and pihon pine extend 
down to 5000 feet and are associated chiefly with dry rock-strewn ledges 
of resistant limestone and sandstone. 

OTHER TYPES OF FOOTHILL TOPOGRAPHY 

While the hogback type of mountain border or foothill topography is 
the predominating one there are a number of other types that require 
examination. They are not all confined to the southern Rockies, but 
are assembled here for comparison with the well-developed foothill 
types of Colorado. The hogback ridges are absent (i) where the 
harder beds rest directly upon the crystalline rocks of the mountain 
slopes, without the presence of a soft valley stratum between the crys- 
tallines and the hard sedimentary formations overlapping them, of 
which some of the foothills on the eastern border of the Bighorns are 
perhaps the best illustrations; or (2) where the upturned edges of other 
sedimentary (Mesozoic) beds are still covered by a capping of younger 
(Tertiary) beds in a horizontal position; or (3) where faulting has 
brought the sedimentary rock in a nearly horizontal position against 
the deformed crystaUines as at Pueblo, Colorado. (4) The eastern 
border of the Rocky Mountains in Montana is developed upon strata 
that have been deformed in such a manner that they dip westward and 
present a reversed border, (a) a single, steep, precipitous, eastern scarp 
overlooking the Great Plains, such as marks the eastern front of the 
Lewis Mountains, Fig. 92, or (b) a series of scarps and flats formed 
upon alternate soft and hard layers — short, steep, eastern slopes and 
long, gentle, mountainward or western slopes. Fig. 93. In the Bighorn 
Mountains and in the Colorado Range, on the other hand, the marginal 
strata in general dip steeply eastward, with the consequence that typi- 
cal hogback ridges are characteristic. (5) Lava flows have occurred 
locally and have caused the formation of a mesa type of topography or 
(6) volcanic cones surmount the eastern border. Besides the hogback 
type six types of foothill topography are thus distinguishable along 
the eastern border of the Rockies. Instead of being everywhere formed 
simply upon the basset edges of the sedimentary beds exposed along 
the mountain flanks, the border has been formed in diverse ways and 
exhibits diverse topographic features. While each of the types indicated 
has distinctive features the first five types are so closely related as not 
to require detailed explanation. The sixth type — the igneous border 
— is well developed in the southern Rockies and has rather complex 
features that merit further consideration. 



360 



FOREST PHYSIOGRAPHY 



IGNEOUS BORDER 



SPANISH PEAKS 



In southern Colorado and locally elsewhere in that state, as at 
Golden, the strata have been deformed or to some extent concealed 
and the border given an unusual character by the occurrence of igne- 
ous masses which in the case of the Spanish Peaks consist of volcanoes 
and associated dikes and lava flows. The type of mountain border 
exhibited is wholly unlike that found anywhere else along the eastern 
face of the Rockies from Alaska to New Mexico. 

The most prominent feature of this kind is the volcanic nucleus 
known as the Spanish Peaks. The two culminating points, West Peak 



w/r^f^f « TfTfWfWWV^ 




Fig. 120. — West Spanish Peak, from the northwest. One of the large dikes of the region is seen in 
the foreground. (U. S. Geol. Surv.) 



and East Peak, are about 2 miles apart and have elevations of 13,623 
feet and 12,708 feet respectively. They rest upon a small platform that 
descends eastward gradually and terminates in an irregular and deeply 
dissected line of steep bluffs that descend abruptly 500 feet to the gently 
rolling plains. The average elevation of this platform is about 7500 
feet. Its surface is a succession of mesa-like ridges and narrow valleys 
of extremely rugged development. The peaks themselves consist of 
stock-like masses occupying nearly vertical fissures, and from them the 
flanking strata dip steeply away with various structural complexities. 
The general ruggedness of the country about them is emphasized by 



ROCKY MOUNTAINS. Ill 361 

many dikes which have a rude radial arrangement with respect to 
the peaks which were the centers of eruption. They were formed in 
crustal fractures related to the deformation of the surface strata, 
deformations produced by the intrusion of great masses of igneous 
rock.^ They are from 2 to 100 feet in thickness. Some of them 
are practically vertical and project above the surface as smooth wall- 
like masses from 50 to 100 feet high. Their crests are sometimes 
straight for long distances, although curved crests are most common. 
They range in length from a few hundred yards to 10 and 15 miles, and 
intersections are common.^ 

The upland portion of the region adjacent to the Spanish Peaks is 
rather heavily timbered and the eastern borders of the plateau support 
a dense growth of pinon and juniper, scattered pines, and scrub oak, 
with occasional park-like openings. The more elevated central, south- 
ern, and western borders support forests of pine; a certain amount 
of spruce, fir, and aspen grows at the base and on the lower slopes. 
The summits of the peaks are from 1000 to 1500 feet above the cold 
timber line. The plains eastward of the plateau upon which the Span- 
ish Peaks stand are practically destitute of timber except for fringes 
of Cottonwood along the running streams. The whole plateau portion 
is subject to frequent summer showers. The summits of the Spanish 
Peaks are rarely free from snow for more than two months in the year, 
while along the narrow valleys cut below the level of the plateau irri- 
gation is necessary, as also upon the surface of the plains country toward 
the east.^ 

NORTH AND SOUTH TABLE MOUNTAIN 

Among the various types of foothill topography one of the most 
important is the fiat-topped mesa type, which is well shown in the 
vicinity of Golden. Here the hogbacks completely disappear and in 
their place are two basalt-capped, sedimentary masses known as North 
and South Table Mountain. They were originally continuous but have 
since been cut through and isolated (Clear Creek). The basalt was 
extruded after the strata had been flexed into steep attitudes and some- 
what eroded. It consists of two fissure flows with no sedimentary rock 
between them.* They protect the underlying beds from erosion; their 
present elevation indicates the degree of dissection that has taken place 
in the vicinity since their formation. 

1 R. C. Hills, Spanish Peaks Folio U. S. Geol. Surv. No. 71, 1901, p. 3, col. i. 

2 Idem, p. 3, col. 4. 

3 Idem, p. I, col. i. 

^ Emmons, Cross, and Eldridge, Geology of the Denver Basin in Colorado, Mon. U. S. 
Geol. Surv. No. 27, 1896, p. 285. 



362 FOREST PHYSIOGRAPHY 

FOOTHILL TERRACES 

The foothill terraces are among the important features on the eastern 
border of the Colorado Range. They are mesalike remnants of stream 
terraces carved in rock, Fig. 118, standing out with special prominence 
along the base of the foothills south of Boulder where they rise from 
100 to 300 feet above the lower plains. They vary in width from a 
fraction of a mile to three miles, and descend eastward with slopes 
varying from 1° to 10°. They appear to be due to a leveling of the 
rock margin of the plains by meandering streams and the deposition 
upon the plains surface of a thin sheet of unassorted gravel.^ The 
terraces always slope toward the streams, with which they once had 
flood-plain relations. 

COLORADO OR FRONT RANGE 

The Colorado or Front Range is the easternmost of the imposing 
chains that form the southern Rockies. Its elevation above the surround- 
ing country is represented in Fig. 121. 

On the north the Colorado Range is a high, heavily timbered, 
plateau-like range separated from the Medicine Bow Mountains by the 
Big Laramie River, and from the Laramie Mountains by the North 
Fork of the Cache la Poudre; but throughout most of its extent it is 
alpine in character, with sharp serrated summits bordered by great 
glacial amphitheaters.^ The broad anticlinal of the range has a very 
flat summit arch, with increasing dip toward the flanks of the anticline 
on the borders of the range. ^ The rocks of the Colorado Range are 
almost exclusively crystalline granites, gneisses, and schists.^ The topo- 
graphic features are not uniform throughout and we shall therefore 
describe them by groups. 

West and northwest of Denver and north of Arapahoe Peak, the 
serrated crest of the Colorado Range is exceedingly formidable, with 
many peaks rising to 13,000 and 14,000 feet. Even the passes are high 
and difficult, and on either side are steep-sided and deep mountain 
gorges. The irregularity of the mountains and their steep descents 
are suggested by the northeast face of Long's Peak (14,270), which 
consists of an almost perpendicular cliff over 3000 feet high which 

1 N. M. Fenneman, Geology of the Boulder District, Colorado, Bull. U. S. Geol. Surv. 
No. 265, pp. 13-15. 

- S. B. Ladd, U. S. Geol. and Geog. Surv. of Colorado and Adj. Terr. (Hayden Surveys), 
1873, P- 436- 

3 Clarence King, U. S. Geol. Expl. of the 40th Par. (King Surveys), vol. i, 1878, p. 21. 

■i Arnold Hague, Rocky Mountains, U. S. Geol. Expl. of the 40th Par. (King Surveys), vol. 2, 
1877, p. 22. 



ROCKY MOUNTAINS. Ill 



363 



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1-^ X 




V 


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PS-M 


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364 



FOREST PHYSIOGRAPHY 




ALLUVIUM 

(BOTTOM LANDS) 



^^ 



I DENVER 

I FORMATION 

BENTON W^S DAKOTA I 

FORMATION P— ^ FORMATION j 

PRE-CAMBRIAN GRANITES GNEISSES 
AND METAMORPHIC ROCKS 



un 



ARAPAHOE ( ' ' ^M LARAMIE 
FORMATION [ ] FORMATION 



I MORRISON 
I FORMATION 



I WYOMING 
1 FORMATION 

(upper DIVISiOhJ 



1 MONTANA I 
! GROUP 1 

I WYOMING I 

1 FORMATION t 

(LOWER division) 



Fig. 122. — Section on the common border of Great Plains and Southern Rockies, showing structure and 
topography and the lava-capped mesas near Golden, North Table, and South Table mountains. 
(U. S. Geol. Surv.) 

extends from timber line (11,000 feet) to the mountain summit. Its 
eastern face presents an almost continuous line of steep-walled amphi- 
theaters; the western side of the range is a zone of high mountains 5 to 
10 miles across which have steep but not precipitous slopes that descend 
to the valley of the Grand and are cut by profound canyons. 



ROCKY MOUNTAINS. Ill 365 

Southward for 12 miles from Arapahoe Peak the topography changes. 
The crest presents a very uniform ridge but httle above timber Hne. 
Like the section north of Arapahoe Peak the eastern face of this sec- 
tion is diversified by amphitheatral valley heads between which are 
broad rounded spurs of such regular descent that wagon roads ascend 
some of them. The western face of this portion of the range is marked 
by massive spurs with rounded forms not separated by canyons.'- 

The whole eastern border of the Colorado Range is usually well defined 
and even sharply defined, and all along it the mountain spurs end 
abruptly. They rise from 5000 or 6000 feet, the level of the border of 
the plains, to 8000 feet at the foot of the main range, and involve a 
belt about 8 miles wide. The streams draining the border have cut 
deep parallel valleys and the intervening ridges therefore have an east- 
west alignment. They are not sharp but massive and have rounded or 
level summits and steep margins. Their crests fall into a general level 
in a quite remarkable manner. On the western border of the Colorado 
Range the descent is also rather abrupt to a general plateau between 
8500 and 10,000 feet high which stretches westward for many miles.^ 

These border plateaus have been studied in detail in the Georgetown 
region west of Denver and their topographic relations clearly defined. It 
has been found that the Colorado Range here exhibits three sets of topo- 
graphic forms: (i) an old, mountainous upland, (2) young V-shaped valleys 
incised in the upland, (3) glacial cirques developed in the valley heads. 

The old upland surface, but little modified by recent erosion, occurs 
in remnants preserved on the ridge crests, which in part accounts for 
their regularity of elevation, form, and alignment. This mountainous 
upland was an ancient land surface whose relief in the preceding topo- 
graphic cycle would be adequately shown by filling the deep valleys 
cut into it.^ Dome-shaped mountains and broad soft-contoured ridges 
stood where sharp peaks and more rugged ridges now are, and the val- 
leys between were broader and less steep than those of the present 
streams. The surface was well adjusted to that of the underlying 
rocks and to their varying resistances to erosion. Precipitous slopes 
were rare and occurred under special conditions, as on the southeastern 
border of the Alps Mountains of Colorado. Shallow valley heads led 

1 F. V. Hayden, U. S. Geol. and Geog. Surv. of Col. and Adj. Terr., 1873, pp. 86-87. 

2 Idem, pp. 88-89. 

3 Spurr and Garey, Geology of the Georgetown Quadrangle, Prof. Paper U. S. Geol. Surv. 
No 63, 1908, pp. 31-36. N. M. Fenneman some time ago called attention to the fact that 
these features appear to indicate an imperfectly base-leveled surface that has been trenched 
by streams invigorated by recent uplift: Geology of the Boulder District, Col., Bull. U. S. 
Geol. Surv. No. 265, 1905. 



366 



FOREST PHYSIOGRAPHY 



down gently from the dome-shaped mountains of the old upland and 
joined wide gentle valleys that were broad and basin-like. All these 
members of the ancient stream systems had normal profiles and no 
reversed slopes existed; consequently lakes did not then exist. -Although 
both normal and glacial erosion have modified this old upland, rem- 




PRESENT TOPOGRAPHY. 



Contour iutKi-val 500 feet 
11106 



THE OLD MOUNTAINOUS UPLAND RESTORED 

10 1 2 3 4 5 miles 

Contour iutei-val 300 feec 
I'JOC 



Fig. 123. — Old mountainous upland of the Georgetown district, Colorado, and present topography. 
(Spurr and Garey, U. S. Geol. Surv.) 

nants of it may still be seen and such remnants bear residual elevations 
and in many places are covered by deep soil, conditions that were 
probably general over the larger portion of the area before uplift and 
glaciation took place, so that rock exposures were comparatively un- 
common except on the steepest slopes.^ 

1 Spurr and Garey, Geology of the Georgetown Quadrangle, Prof. Paper U. S. Geol. Surv. 
No. 63, igo8, p. 52. 



ROCKY MOUNTAINS. Ill 367 

The mountainous upland of the Colorado Range, formed in late 
Tertiary time, was then uplifted and tilted eastward so that valley carv- 
ing was begun. Canyons of considerable size were opened up before 
the glacial period and these the streams are still enlarging. Clear 
Creek is in places 2^ miles wide, while the gorges along the Deer, Elk, 
and Bear creeks, all in the eastern slope of the range, are in general not 
more than one-half mile wide. The valley walls approach each other 
upstream and the valleys linally become narrow V-shaped notches in 
the old upland surface. Rock projects from the valley sides and huge 
bowlders lie along the courses of the swift streams. The old upland 
surface is comparable with similar uplands (a) in the vicinity of Pikes 
Peak,^ (b) in the Sierra Madre Mountains of south-central Wyoming,^ 
(c) remnants of an ancient surface widely distributed over other por- 
tions of Colorado,^ and (d) mature profiles widely developed in other 
portions of the Rockies as in western Montana, p. 318. The character 
of the old mountainous upland is brought out clearly in the maps of 
the Hay den Surveys of 1877, where the summits of the long table- 
topped spurs of various plateau and mountain groups appear to indi- 
cate a rather general development of moderate slopes. All of these 
surfaces are approximately contemporaneous and of late Tertiary age. 
The mountainous surface is now exposed only in remnants on the spur 
tops and in certain of the unglaciated valleys. 

The present-day expression of the detailed topography of the Colo- 
rado Range west of Denver is affected rather intimately by the char- 
acter of the rock wherever dissection has partly destroyed the older 
graded surface. The country underlain by schists has very distinctive 
topographic qualities. Where the dip of the schistosity is low, smooth- 
contoured slopes are developed upon the exposures ; where it is approxi- 
mately vertical the topographic forms are craggy and serrate as on the 
north side of Chief Mountain. The gneisses weather into exposures 
which at a distance have the bedded aspect of sedimentary rocks except 
where there is a prominent development of joints. The rugged crags 
found almost continuously along stream valleys carved in gneiss are 
controlled in their minor details by rectangular joint systems and have 
very characteristic features. Turrets and buttresses and castellated 
forms are seen throughout the area covered by the granite-pegmatite, 
which is one of the most resistant massive rocks of the region. 

1 W.. Cross, Mon. U. S. Geol. Surv., vol. 27, p. 202. 

2 A. C. Spenser, Prof. Paper U. S. Geol. Surv. No. 26, 1904, p. 12. 

' F. V. Hayden, U. S. Geol. and Geog. Surv. of the Territories, Atlas of Colorado, 1877, 
Sheets S, 6, 7. 



368 FOREST PHYSIOGRAPHY 

Below timber line the granite weathers into typical dome-shaped 
forms, the domes being from 200 to 300 feet high and from 300 to 
400 feet in diameter; above timber line the domes are absent owing to 
the strong temperature changes and their shattering effect.^ 

In the Pikes Peak district of the Colorado Range the chief top- 
ographic feature is a great plateau developed upon granite and gneiss 
and modified by large extrusions of volcanic rock that form mountains 
upon it. Sedimentary beds, formerly of greater extent, are now con- 
fined chiefly to the borders of the tract and to small local basins on 
the plateau.^ 

GLACIAL FEATURES 

The higher parts of the main ranges of Colorado were for the most 
part covered with ice during the last glacial epoch, only the narrow 
crests of the inter-valley ridges projecting above the glacial cover. 

The ice was deepest and most powerful in the larger mountain val- 
leys down which it extended as valley glaciers for great distances, in 
some cases out over the piedmont plains or plateaus below. ^ The 
number of glaciers which existed in the Colorado Range during the 
glacial epoch may be appreciated by the fact that within the Lead- 
ville quadrangle alone, p. 371, there were 26 large glacial systems and 
II smaller ones, or 37 in all, in an area of 945 square miles.'' The 
glaciers ranged in elevation from a minimum height of 8800 feet 
to a maximum height of 13,700 feet. Since- many peaks of the Park 
Range reach elevations approximating 13,000 feet it follows that all the 
larger valleys were occupied by glaciers. The larger and more vigor- 
ous glaciers developed on the eastern slopes, a condition due probably 
to the greater size of the preglacial valleys rather than to any advan- 
tages of exposure or precipitation. As a result of glaciation in the 
Colorado Range cirques and glacial lake basins were formed. The 
cross sections of the valleys were developed into a pronounced U shape, 
so that a shoulder now occurs between a lower, younger, and slightly 
modified glaciated portion and an upper, older, unglaciated portion. 
The floors of both cirques and glaciated valleys are very uneven and 

1 Spurr and Garey, Geology of the Georgetown Quadrangle, Col., Prof. Paper U. S. Geol. 
Surv. No. 63, 1908, pp. 35-36. 

2 W. Cross, Pikes Peak Folio U. S. Geol. Surv. No. 7, 1894, p. 3. 

3 The extent of any glacier depends upon the following features: (a) the height of the sur- 
rounding mountains; (6) the shape and size of the catchment basins; (c) the number and size 
of the tributary valleys; {d) the slope and shape of the valley floor; (e) the exposure; and (/) the 
precipitation. 

* S. R. Capps, Jr., Pleistocene Geology of the Leadville Quadrangle, Col., Bull. U. S. Geol. 
Surv. No. 386, 1909, p. 9. 



ROCKY MOUNTAINS. Ill 369 

smooth rock ledges protrude above the till. Lateral moraines, some- 
times double, form prominent narrow ridges of till on either side of the 
A'alley walls and are here the most striking types of glacial deposits. 
The terminal moraines have an irregular surface marked by hillocks, 
ridges, and depressions and many of them have very steep fronts over 
which the streams descend in a succession of waterfalls. The cirques 
are the most striking feature of glacial erosion in the region; the deepest 
are in the vicinity of Mount Evans, where one cirque wall rises 1 700 feet 
in less than a mile. The steeper cirques have bare, rocky, unscalable 
walls and frequently have postglacial talus accumulations along their 
bases. Some of them are compound, as in the case of the three well- 
defined cirques at different elevations in the valley of the stream that 
heads in Summit and Chicago lakes, a mile west of Mount Evans. 
In a number of cases a knife-edge ridge or arete was formed by the 
headward erosion of two cirques on opposite sides of a divide in the 
mountainous upland. 

TREE GROWTH 

The main portion of the Colorado Range was heavily timbered below 
the cold timber line (11,250 to 12,000 feet) when the valleys of the 

^ Colorado 
Sawatch o Range 
Wasatch Mts. c Mts. P « 

Great $ 'i 2 2c « ^ ,Pm200'^^-^^ Great Plains 

Basin = ,.l!ir\ , « "^^ ^ .C^^~;';>>-<>e<\ ^ 10000' 




m;; 7.5 in. /./ in././ in, B.y in. v.,r>. . 

W////////)i//////////////A///M//////////////)^^^^^ 



Fig. 124. — Topographic profile and distribution of precipitation across the Wasatch and the southern 

Rockies. 

region were first settled. At altitudes over 8500 feet western yellow 
pine and Douglas spruce grow on dry areas. On higher and moister 
ground lodgepole pine and Engelmann spruce are found; these are 
superseded in turn by dwarf spruce and finally near timber line by 
mountain white pine. Large areas have been burned over and are now 
covered with second-growth lodgepole pine and aspen. Above timber 
line there is an alpine flora of many species.^ 

PARK RANGE 

North of the Grand River Valley the Park Range is not high and 
rugged but a great, rolUng, heavily timbered, even-contoured plateau of 

1 Spurr and Carey, Economic Geology of the Georgetown Quadrangle, Col., Prof. Paper 
U. S. Geol. Surv. No. 63, 1908, pp 30-31. 



370 FOREST PHYSIOGRAPHY 

crystalline rock with massive marginal slopes. For 50 miles south of 
the Grand River Valley its character is entirely different. The sum- 
mit ridges are rugged and sharp and bordered by great amphitheaters 
with steep, cliffed sides. Deep glacier-scored canyons alternate with 
the secondary ridges; at their mouths are belts of morainic drift formed 
by ancient glaciers whose courses were the present valleys or canyons 
and whose neve fields occupied the existing amphitheaters of the valley 
heads. ^ Glacial action was carried so far that parts of the range were 
thoroughly skeletonized. Some of the eastern spurs are flat-faced and 
have gentle descents. At the higher elevations the western slopes are 
precipitous being formed upon hard crystalline rock, but at lower ele- 
vations where sedimentary rock occurs they become gentler. On both 
flanks of the range the sedimentary formations seldom rise more than 
a few hundred feet above the bordering plains and plateaus. The cul- 
minating summits of the range are of granite." In structure the Park 
Range is a great overthrust extensively eroded. The movement was 
directed westward, hence the western border is abrupt, for it has been 
developed upon the edges of the overthrust beds in a manner in some 
respects similar to the eastern border of the Lewis range of Montana 
(p. 311).^ The highest peaks are much lower than those of the Colorado 
Range; Mount Zirkel alone reaches above 12,000 feet, and this in spite 
of the equivalent elevations of the main summits of the two ranges.* 

TREK GROWTH 

The Park Range is covered with large timber similar to that found 
on the Colorado Range. The main types are pines above and aspens 
and small low trees along the lower or dry timber line. In the local 
alluvium-floored basins timber is wanting, as in Egeria Park and the 
parks along the Yampah, except for a fringe of cottonwoods bordering 
the streams.^ 

SAWATCH RANGE 

The Sawatch Range extends for over So miles from the Mountain of 
the Holy Cross (lat. 39° 28') southward to the San Luis Valley. "For 
this entire distance [it] literally bristles with lofty points about 10 of 
which rise above 14,000 feet and many more are 13,000 feet above sea 

1 Hayden Reports, 1873, pp. 178, 18S, 189, 436, 437. 

2 Idem, pp. 65-66. 

3 Idem, 1874, p. 71. 

* Arnold Hague, U. S. Geol. Expl. of the 40th Par. (King Surveys), vol. 2, 1877, pp. 130-132. 
5 S. B. Ladd, U. S. Geol. and Geog. Surv. of Col. and Adj. Terr. (Hayden Surveys), 
1874. P- 441- 



ROCKY ■ MOUNTAINS. Ill 



371 




Scale of Miles 



Fig. 125. 



• Extent of the former glacier systems in parts of the Park, (east) and the Sawatch (west) 
ranges of Colorado, Leadville quadrangle, (After Capps, U. S. Geol. Surv.) 



372 FOREST PHYSIOGRAPHY 

level." It has a rather symmetrical outline, and its pointed summits 
vary but little in either form or height.^ On the east is the valley of the 
upper Arkansas; on the west is the valley of the Gunnison. Like the 
neighboring ranges on the north and east it is a great anticlinal uplift 
whose central axis is composed of crystalline rocks from which sedi- 
mentary formations dip away at various angles. This type of structure 
is, however, complicated on the southwestern flank of the range by 
volcanic flows which wrap about the Sawatch crystallines, as the 
Cachetopa Hills — a portion of the great igneous field of the San Juan 
region. Because of this and other structural irregularities, the range is 
not so simple as the Park and Colorado ranges, and is still more irreg- 
ular in the southeastern extension of this mountain axis known as the 
Sangre de Cristo Mountains. 

The higher portions of the Sawatch Range have been glaciated in 
common with the other high ranges of Colorado. Glacial cirques or 
headwater amphitheaters were developed and peaks trimmed to sharp, 
sometimes pyramidal outlines. 

La Plata peak in the Sawatch Range has been glaciated to such an extent that it now stands 
as a sharp peak between the encroaching heads of three glacial channels. Its steep slopes 
merge into the steep slopes of the glacial cirques that occur northwest, southwest, and east of 
the peak. The forms of the mountain are all sharp in contrast to the rounded forms of the 
unglaciated lower portions of the adjacent mountains. Mount Elbert may be cited as a type 
of peak in which the glacial cirques have not encroached so far and where the summit of the 
mountain still retains a massive dome-like outline such as La Plata Mountain had before the 
erosion on its flanks had been carried so far.2 



SANGRE DE CRISTO RANGE 

The Sangre de Cristo Mountains, Fig. 117, rise abruptly on the east 
from Wet Mountain Valley and Huerfano Park, among the larger parks 
of Colorado, and on the west from the San Luis Valley. They are from 
12,000 to 14,000 feet high with from 3000 to 5000 feet relative altitude. 
The range follows an almost straight line for 40 miles and presents a 
very imposing sight, the dark color of the rock bringing out its relief to 
advantage. Its average width is not much over 10 or 12 miles, which 
is small compared with its length and altitude. The range extends 
southward to Sangre de Cristo Pass, and beyond this point the axis of 
elevation extends to and beyond the New Mexico boundary to Santa Fe, 
where it ends in a number of minor ranges. 

1 Hayden Surveys, 1874, P- 54- 

2 W. M. Davis, Glacial Erosion in the Sawatch Range, Col., Appalachia, vol. 10, iSgg, 
p. 403. 



ROCKY MOUNTAINS. Ill 373 

North of Poncha Pass the Sangre de Cristo Range is a true sierra. 
The Sierra Blanca group of peaks, for example, have a serrate and 
jagged crest Hue; their precipitous front rises abruptly from the fiat San 
Luis plain to heights of more than a mile, thus giving the range a bold 
and majestic appearance.^ 

The Sangre de Cristo Range is a great and somewhat complex anticline. 
In general the axis of the range consists of intrusive granite flanked on 
both sides by conglomerate chiefly and also by sandstone, shale, and 
limestone. Faulting has locally caused the sedimentary formations to 
abut squarely against the basal granite.- In places the faults trend at 
an angle with the main axis of the anticlinal uplift, a structure that 
causes the topographic condition of offsets that diversify the mountain 
border.^ Local variety is given the border relief by dikes of igneous 
rock which traverse the flanking sedimentaries. The streams have cut 
deep gorges in the upturned sandstones and limestones; steep bluffs 
occur along the valley sides and only an occasional patch of flat land 
occurs on the valley floors."* 

WESTERN BORDER RANGES 

The eastern and central divisions of the southern Rockies are char- 
acterized by the presence of granitic masses and extensive areas of meta- 
morphic schists typically represented in the Colorado and Park ranges. 
But in the westernmost ranges of the district vast quantities of volcanic 
material have been extruded, which have in many notable instances pro- 
foundly modified the topography. The San Juan, La Plata, Needle, and 
Elk mountains may be taken as typical illustrations. They are so rugged 
and access to them is so difiScult that permanent settlements have been 
formed in very few places. There are few trails, and at great distances 
from each other are scattered prospectors' cabins, now commonly 
deserted.^ 

1 C. E. Siebenthal, Geology and Water Resources of the San Luis Valley, Col., Water- 
Supply Paper U. S. Geol. Surv. No. 240, 1910, pp. 34-35. 

2 Idem. 

2 For structural features see J. J. Stevenson, The Geology of a Portion of Colorado, U. S. 
Geog. Surveys West of the looth Meridian (Wheeler Surveys), vol. 3, 1875, pp. 490 et seq. 

* F. M. Endlich, U. S. Geol. and Geog. Surv. of Col., and Adj. Terr. (Hayden Surveys), 
1873. PP- 323 ff- 

5 So little known is the region that during the survey of the Needle Mountains quadrangle, 
in 1900, a large number of peaks and other prominent features were given names for the first 
time. 



374 FOREST PHYSIOGRAPHY 

SAN JUAN MOUNTAINS 

The term " San Juan region," Fig. 117, is generally applied to a large 
tract of mountainous country in southwestern Colorado and an ad- 
jacent zone of undefined lower country bordering it on the west and 
south. The greater part of the district is a deeply scored or dissected 
plateau drained on the north by branches of the Gunnison, on the west 
by branches of the Dolores and San Miguel, on the south by the San 
Juan, and on the east by the Rio Grande; the eastern part consists of 
high tablelands that represent old plateau surfaces; the San Juan 
Mountains proper extend from the great plateau- region of Colorado and 
Utah on the west to San Luis Park on the east and from the canyon of 
the Gunnison on the north to the rolling plateaus of New Mexico on the 
south. They have a length of 80 miles east and west and a north- 
south width of nearly 40 miles, their summits forming a great group 
rather than a range. The elevations of the highest peaks exceed 14,000 
feet, and hundreds of peaks exceed 13,000 feet. Some of the valleys 
in the heart of the mountains haye been cut down 9000 feet or more, 
and the configuration^ especially on the west, is extremely rugged and 
presents an almost infinite variety of slopes. Several of the small groups 
of high peaks in the border zone have special names, such as Needle 
Mountains on the south, La Plata and Rico mountains on the south- 
west, and San Miguel Mountains on the west. The geologic structure 
and to a certain extent the topographic character of the bordering 
groups are sufficiently unlike the San Juan Mountains to constitute 
them subordinate topographic divisions. 

The southwestern border of the San Juan Mountains is marked by 
bluffs with vertical faces where the great upland crowned by moun- 
tains descends to the Navajo, San Juan, Piedra, and adjacent stream 
courses, Fig. 117. When viewed from this direction the upland appears 
as a rugged range, but at the general summit level its true character as 
a great plateau crowned by isolated summits becomes apparent. The 
relatively unbroken character of the surface over a considerable number 
of summit areas prevents thorough drainage, and swamps abound above 
timber line. 

A special feature of the San Juan region remarkably developed in the 
San Juan Mountains and in many places in the Needle Mountains is 
the large number of landslides determined by the alternation of soft 
shale and beds of limestone or sandstone. They consist of great 
blocks of rock tilted at various angles, with fine material collected in 
the intervening spaces, and have very uneven surfaces without regular 



ROCKY- MOUNTAINS. Ill 



375 



drainage systems. Stagnant pools and morasses alternate with deep 
trenches. The slides occur at the heads of the ravines and on the sides 
of the steep ridges separating the smaller valleys.' 

The landslides of the Telluride and Rico districts of the San Juan 
region are supposed to have been caused in part by earthquake shocks 
on such a prodigious scale that the sliding and fracturing of solid rocks 
occurred. Possibly also the melting of supporting ice masses after they 
had deepened the valleys and steepened the valley slopes may have 




Fig. 126. — Landslide surface below Red Mountain, near Silverton, Colorado. 

added to the effect of the structural conditions.^ Earthquake shocks 
have occurred in recent years in the Telluride and Red Mountain dis- 
tricts within the landslide area, and fresh fractures have also been 
observed in the Red Mountain mines. ^ In the Telluride region the 
rocks involved in the landslides have been those of the volcanic series 
which rest upon soft Cretaceous shales.* 

1 Ernest Howe, Landslides in the San Juan Mountains, Colorado, Prof. Paper U. S. Gaol. 
Surv. No. 67, 1909. 

- Cross and Howe, Silverton Folio, Col. U. S. Geol. Surv. No. 120, 1905, p. 25, col. i. 

3 H. C. Lay, Trans. Amer. Inst. Mining Engineers, vol. 31, 1902, pp. 558-567. 

* F. L. Ransome, A Report on the Economic Geology of the Silverton Quadrangle, Col., 
Bull. U. S. Geol. Surv. No. 182, 1901, pp. 27-28, et al. 



376 FOREST PHYSIOGRAPHY 



RAINFALL AND VEGETATION 



The San Juan Mountains are surrounded by arid country, but they 
themselves have an abundant precipitation, the higher peaks and basins 
being seldom entirely free from snow. The abundant water supply 
supports a heavy forest growth in many localities upon the western 
and northern slopes. The upper timber line lies between 11,500 and 
12,000 feet, and as a consequence large areas in the lofty interior of the 
San Juan Mountains are without tree growth, although a low alpine 
flora is found in favored situations. Spruce and aspen cover the higher 
slopes, and below them white pine, scrub oak^ pnion pine, and cedar 
are found. On the great volcanic plateau of the San Juan region the 
precipitation is less and supports only an herbaceous vegetation. 
Prominent yet low cone-shaped peaks present a more des6late appear- 
ance and are sometimes so strewn with rock fragments as not to support 
plants of any sort. High plateaus of volcanic rock appear in places with 
a grassy vegetation so different from the forests on the older sedimentary 
and igneous rock to the east and locally in the deep canyons of the vol- 
canic area, as to form in a certain sense a guide to the geologist.^ 



LA PLATA MOUNTAINS 

The La Plata Mountains are located between the well-watered, well- 
forested San Juan Mountains and the arid mesa, plateau, and canyon 
country that extends into Utah, Arizona, and New Mexico. The La 
Plata Mountains are a dissected dome and their drainage systems have 
a radial arrangement. Many of the peaks rise a thousand feet or more 
above timber line and are characteristically rugged.' On the west 
the slopes descend rather steeply 4000 or 5000 feet to the rolling plain 
known as the Dolores Plateau, deeply dissected by a number of deep 
canyons, Fig. 78. The simple character of the La Plata Mountains is 
complicated on the western and northwestern sides by intruded igneous 
rocks which occur in soft shales overlying sandstone, the intrusive rock 
having prevented the uniform erosion of the shales. On the southwest 
the dip of the slope of the sandstone is uninterrupted between 8000 and 
10,000 feet, and the descent in this quarter is regular and broad. The 
intrusive rock is for the most part porphyry, and the masses are large 
enough to cause peaks or ridges which appear as irregularities in the 

1 F. M. Endlich, U. S. Geol. and Geog. Surv. of Colorado (Hayden Surveys), 1873, p. 306. 
» Cross and Spencer, La Plata Folio U. S. Geol. Surv. No. 60, 1899, p. i. 




Fig. 127. — Looking down La Plata Valley from the divide at the head of the valley. The steep slopes 
\ are characteristic. Landslide in left foreground. (La Plata Folio U. S. GeoL Surv.) 




Fig. 128. — Western summits of La Plata Mountains from the divide at head of La Plata Valley. This 
view is panoramic with the view above. It shows the rugged summits within the eroded volcanic 
stocks of the mountains. Diorite Peak on left. (La Plata Folio U. S. Geol. Surv.) 

377 



378 FOREST PHYSIOGRAPHY 

general slope of the dome. The porphyries occur as sheets or small 
laccoliths; ^ later intrusions took place which cut the sedimentary beds 
and the sheets of porphyry forming stocks which constitute several of 
the highest peaks of the La Plata Mountains. 

In connection with the formation of the dome of the La Plata Mountains a number of faults 
were developed but these are neither numerous nor important. The upthrust is commonly 
on the side near the center of the dome and has resulted in the formation of a number of steep 
slopes facing southward .2 

The arid plains or plateaus rising west of the La Plata Mountains 
support a growth of white pine, piiion, and cedar, transitional between 
the barren expanses of the plateau and the forested slopes of the La 
Plata Mountains. In general the heaviest timber grows on the western 
and southern slopes since it is from those directions that the winds 
commonly blow. The forests extend up to 11,500 and 12,000 feet; the 
growth consists of spruce, fir, and aspen; above the timber line there 
is a scanty vegetation of alpine character.^ 



NEEDLE MOUNTAINS 

The rocks composing the Needle Mountains are chiefly granite, schist, 
and some c^uartzite. Four of the summits exceed 14,000 feet in eleva- 
tion and many exceed 13,000. Some of the mountains are deeply dis- 
sected and extremely bold. North of the Needle Mountains is the 
great curve of the Grenadier Range, which is chiefly of quartzite.; on 
the north and east the surface is almost entirely covered by volcanic or 
other rocks; on the south sedimentary rocks were laid dowm upon a 
pre-Paleozoic land surface of moderate relief now exposed (by the 
removal of the sedimentary cover) in the form of a southward-sloping 
tableland consisting of isolated mesas between deep-cut valleys. There 
is thus afforded a very strong contrast between the sharp peaks and 
needles of the Needle Mountains and the comparatively low relief 
of the reexposed and ancient land surface extending southward from 
them.* 

Of great topographic importance was the formation (Tertiary) of 
three series of volcanic accumulations: (i) a tuff which attained a thick- 
ness of 3000 feet east of Ouray (San Juan), (2) lava flows, tuffs, and 
agglomerates (Silverton Series), also reaching a thickness of about half 

1 Cross and Spencer, La Plata Folio U. S. Geol. Surv. No. 60, 1899, p. S, col. i. 

2 Idem, p. 10, col. 3. 

3 Idem, p. 2, col. i. 

* Cross and Howe, Needle Mountains Folio U. S. Geol. Surv. No. 131, 1905, p. i, cols. 2-3. 



ROCKY MOUNTAINS. Ill 



379 



a mile in places; and (3) later thin lava flows and tuff of a third period 
of volcanic activity (Potosi Series). In connection with the formation 
of these materials there were intruded into the sedimentary rocks various 
dikes, sills, laccoliths, and irregular masses which are the deeper-seated 
equivalents of the surface volcanics. 

On the flanks of the Needle Mountains dome a simple consequent 
drainage was developed during the doming period. The southern flanks 



-^^, 




Fig. 129. — Mount Wilson group in background. Looking down Howard Creek from south of 

Ophir Pass. 



of the dome were not covered with volcanic material and the conse- 
quent drainage developed on these slopes was not affected by volcanic 
action. The northern slopes of the domes, on the other hand, were 
affected by volcanic outpourings and the drainage greatly modified. 
After the last great eruptions the streams proceeded to dissect the 
surface deeply. 

The consequence of further upHft of the region and resulting deep dissection has been 
the formation of a confusing variety of slopes in intimate relation to the detailed geologic 
structure. Within short distances of each other one may find (i) ancient granites, (2) sedi- 
mentaries of more recent origin, (3) Tertiary conglomerates, and (4) more recent volcanic 
accumulations. The development of slopes upon these varied rocks has naturally been very 
complex and few generalizations may be applied to individual mountains or to the group as a 
whole. 





38o 



Fig. 130. — Part of Needle Mountains, Colorado. Grenadier Range on west, White Dome in center; 
about the head of Vallecito Creek. These two views are panoramic with each other. 



ROCKY MOUNTAINS. Ill 381 

GLACIAL FEATURES 

A phase of the recent dissection of the region is associated with gla- 
ciation; the conditions prevaihng in the Needle Mountains during the 
portion of the glacial period of which the best records are left were 
nearly the same as those which exist in the Alps at the present time. 
From the positions of well-defined terminal and lateral moraines it is 
inferred that during the last recognized period of glaciation alpine glaciers 
descended the more favorably located valleys some 25 miles. The rock 
debris in the terminal moraines consists largely of material derived from 
the Needle Mountains. The higher and sharper peaks and ridges were 
not buried beneath ice and snow, but at lower elevations the bare rock 
surfaces are grooved and polished and indicate vigorous glacial action. 

ELK MOUNTAINS 

The principal range of the Elk Mountains lies north of the San Juan 
region and west of the northern end of the Sawatch Range. The moun- 
tains have great diversity of color, due to the presence of light-gray 
trachyte, red, maroon, and brown sandstone, etc. They are from 13,000 
to 14,000 feet high, and are characterized by sharp, conical peaks and 
ragged, serrated ridges, pinnacles, and spires. The main range is bor- 
dered throughout a large part of its extent by broad, high, flat-topped 
spurs or secondary ranges.^ It is about 40 miles long and dissected 
by gorges and canyons whose extreme ruggedness and picturesqueness 
are owing to the complicated structure, the variegated rocks, and the 
youthfulness of the forms themselves. Enormous amphitheaters at the 
heads of the bordering valleys have been cut back so far as to give 
the main crest a zigzag course and to make it so narrow as to be almost 
impassable.- 

PARKS OF THE SOUTHERN ROCKIES 

Between the two main ranges of the Rockies in Colorado is a line of 
basins of exceptional interest. The three northernmost, North, Middle, 
and South parks, are geologically a unit. Their southern continuation 
is not San Luis Park, as generally supposed, but Wet Mountain Valley 
and Huerfano Park between the front range axis on the one hand and 
the Sangre de Cristo axis on the other. The San Luis basin lies between 
the latter axis and the Sawatch Mountains. The former depression 
began to take shape at least as far back as the Triassic; the San Luis 
Valley is occupied chiefly by late Tertiary and Pleistocene sediments.* 

1 H. Gannett, U. S. Geol. and Geog. Surv. of Colorado and Adj. Terr. (Hayden Surveys), 
1874, P- 417- 

- Hayden Surveys, 1874, pp. 58, 71. 

' C. E. Siebenthal, The San Luis Valley, Colorado, Science, n. s., vol. 31, 1910, p. 745. 



382 FOREST PHYSIOGRAPHY 

San Luis Park is the largest of the five main parks of Colorado. It is 
in many respects like the Sage Plains of the Green River Valley or the 
valley of the San Joaquin in California, consisting of a depression floored 
by young sedimentary strata and still younger alluvium; the lost rivers 
on the piedmont alluvial plain flanking the mountainous margin of the 
basin are also characteristic. Each of these parks drains to the sea by 
way of a stream which cuts through a deep mountain gorge on the margin 
of the basin. North Park is drained by the Platte, South Park by the 
South Platte, Middle Park by the Grand, and in the mountains enclosing 
San Luis Park the southward-flowing Rio Grande takes its rise. These 
parks are all the more striking because they lie in the midst of a very 
rugged mountain region. Their unique character is due primarily to 
broad intermont structural depressions whose low relative elevation 
and high outlets have made them the seat of aggradation, not dissec- 
tion, while the neighboring uplifts are among the loftiest ranges in the 
country and have been profoundly dissected, giving rise to a rugged and, 
locally, even an alpine topography. With these general relations in 
mind we shall now note briefly the special features of each park. 

NORTH PARK^ 

North Park, 7500 feet above the sea, is nearly quadrangular in shape; 
it is about 50 miles in extent from east to west and 30 miles across from 
north to south. Its surface, although somewhat rugged, is marked by 
broad bottoms along the streams, especially the North Platte and its 
tributaries. The lofty and, for a part of the year, snow-covered moun- 
tains enclosing it like a gigantic wall, are covered with a dense growth 
of pine, but scarcely a single tree may be found over the whole 1500 
square miles of the park itself save along the stream courses. Grass is 
found in abundance, and the park was originally the feeding ground of 
thousands of antelopes. The bordering strata dip under the park, becom- 
ing nearly or quite horizontal toward its center. In this respect North 
Park resembles the three other major parks of Colorado in being pri- 
marily a great structural depression sufficiently free from mountain- 
ous elevations and hence sufficiently drier to form a striking contrast to 
the high forest-clad country about it. 

MIDDLE PARK 

Although Middle Park has on the whole a basin-like aspect, yet in 
detail this feature is often lost in the prominence of many of the ridges 
separating its secondary drainage lines. In this respect it is in sharp 

1 F. V. Hayden, U. S. Geol. Surv. of the Terrs., 1867, 1868, and 1869, pp. 87-88. 



ROCKY MOUNTAINS. Ill 383 

contrast to both North and South parks on either hand. The basin is 
unique in being the easternmost region in the United States where Pacific 
waters take their rise; it drains westward through the Grand River to 
the Pacific. The borders of the basin are composed of crystalHne 
schists and granites on the eastern, southern, and western sides, while 
the northern border as well as much of the floor of the basin is com- 
posed of younger sedimentaries.^ 

SOUTH PARK 

South Park is about 45 miles long and about 40 miles wide at its 
widest portion near the southern end. Its elevation at the north is 
about 9500 feet, at the south about 8000 feet. Its surface is regular only 
by contrast with the more rugged country surrounding it. Numerous 
parallel ridges with northerly trend cross the park and make its surface 
irregular. At the southern end are many isolated buttes, most of them 
of volcanic origin. Portions of the park are underlain by rather flat- 
lying sandstone, as is the case with San Luis Park, and such portions 
have as a rule a more uniform surface than the rest.- 

SAN LUIS PARK 

The San Luis Valley basin owes its origin primarily to the broad, 
gentle, trough-like depression of its underlying sandstones. In late 
geologic time it probably contained a lake of considerable extent, a 



SAN LUIS VALLEY 




Santa te tormalion 



■ Lava 

, , ^proximate scale ^ („„ ,3,3) 

5 5 Miles 




Fig. 131. — Cross section of San Luis Valley from foot of Blanca Peak to foot of Conejos Range. 
(Adapted from Siebenthal, U. S. Geol. Surv.) 

condition inferred from the character of the fine sediments accumulated 
in it.^ The draining of the lake by the cutting down of the outlet 
stream, the building up of great alluvial fans, among which that of the 
Rio Grande is the largest, and the deposition of glacial deposits locally 
about its border are still later occurrences of physiographic importance. 

1 Emmons, Cross, and Eldridge, Geology of the Denver Basin in Colorado, Mon. U. S. Geol. 
Surv. No. 27, 1896, p. 4. 

- A. C. Peale, U. S. Geol. and Geog. Surv. of Col. and Adj. Terr. (Hayden Surveys), 1873, 
p. 212. 

3 F. M. Endlich, U. S. Geol. and Geog. Surv. of Col. and Adj. Terr. (Hayden Survej^s), 
1873, pp. 334, 339- 



384 



FOREST PHYSIOGRAPHY 



San Luis Valley appears nearly level over great areas but in fact it 
departs from the horizontal by important amounts. The marginal 
slopes descend by regular gradients to an axial depression located well 
toward the eastern margin of the valley; they are developed upon a 
series of coalescing alluvial fans and the longest and flattest slopes are 
those built by the largest streams; the Rio Grande has built an alluvial 
fan so large as to throw the axis of the valley to one side (east) of the 
center of the depression.^ The eastern side of the basin is bordered by 




Fig. 132. — Looking eastward from Hunt Springs across the north end of San Luis Valley; San Luis 
Creek in the middle distance, Sangre de Cristo Range in the background. (Siebenthal, U. S. Geol. 

Surv.) 



the Sangre de Cristo Range, on whose flanks a great alluvial plain has 
been formed whose deposits above an elevation of 9000 to 9500 feet 
consist of fluvio-glacial debris formed in connection with Pleistocene 
glaciers. Concentric terminal moraines surmount the crests of the 
alluvial fans and cones, Fig. 131.^ 

1 C. E. Siebenthal, Geology and Water Resources of the San Luis Valley, Col., Water- 
Supply Paper U. S. GeoL Surv. No. 240, 1910, p. 10. 

2 C. E. Siebenthal, Notes on Glaciation in the Sangre de Cristo Range, Colorado, Jour. 
Geo!., vol. 15, 1907, p. 15. Idem, The San Luis Valley, Colorado, Science, n. s., vol. 31, 1910, 
p. 746. 



ROCKY- MOUNTAINS. Ill 385 

Northeastward from Antonito there stretches a line of flat-topped to rounded basaltic hills 
which represent late flows upon the alluvial floor of the valley. They form the chief topo- 
graphic break in the continuity of the basin floor. The smooth valley surface is also inter- 
rupted in a number of localities by sand dunes. The highest occur between Medano and 
Sand Creek and these also cover the most extensive single tract, 40 square miles. They con- 
sist of rather coarse, white, quartzite sand blown into place by the heavy southwest winds that 
occasionally blow for a two or three day period across the valley. Elsewhere the sand is com- 
monly blown out of place between patches or clumps of bush and grass, leaving small hollows 
or basins that contain lakelets in the wet season. 1 



OTHER TYPES OF PARKS 

Besides these large intermont parks there are scores of smaller ones. 
They have been formed in at least four main ways, (i) San Luis 
Park, as we have seen, is a broad structural basin drained by the Rio 
Grande River, and the same is true of North, South, and Middle 
parks. (2) In the Pikes Peak region and specifically in the south- 
central portion of the Pikes Peak quadrangle, is a depression known as 
Shaw's Park; it is formed upon sandstones, marls, and limestones in the 
form of a syncline whose margins have been in a number of cases down- 
faulted in a pronounced manner. The weathering of the softer sedi- 
mentaries has accentuated the flatness of the depression normal to the 
synclinal structure and thus developed a lowland 5 or 6 miles in width. 
A similar park has been developed under similar structural conditions 
immediately west of Shaw's Park and is known as Twelve Mile Park. 
(3) A third type of park may be seen very commonly throughout the 
region, a typical occurrence being Low Park, shown in the Needle Moun- 
tains topographic sheet, in the valley of the Florida River, where a 
broad valley lowland is formed by combined glacial erosion and the 
present drainage.^ Similar valley lowlands of small extent are not un- 
common at the junction of tributary and master streams and are com- 
monly known as "parks." (4) A fourth type of park is described by 
Powell,^ who calls attention to the fact that the great anticlinal folds in 
the Park Mountains have a north-south trend and that on the flanks 
of each fold there is developed a zone of maximum dip so that the rocks 
at the flanks of the ranges are turned abruptly down. In such cases 
small parks are formed by the wearing out of the softer beds, leaving 

1 C. E. Siebenthal, Geology and Water Resources of the San Luis Valley, Col., Water- 
Supply Paper U. S. Geol. Surv. No. 240, 1910, pp. 47-48. The detailed features of the San 
Luis basin are represented in Sheet 10, Atlas of Colorado, Hayden Surveys, where the course 
of the Rio Grande is shown as well as the course of San Luis, San Isabel, and other creeks 
which empty into San Luis Lake instead of having a surface channel to the Rio Grande. 

- Pikes Peak Foho U. S. Geol. Surv. No. 7, 1894. 

3 Physiography of the United States, Nat. Geog. Soc. Monographs, 1896, pp. 88-89. 



386 FOREST PHYSIOGRAPHY 

the harder strata standing as great steep walls parallel to the axes of 
the principal ranges. The famous Garden of the Gods near Pikes Peak 
is explained in this way. 

TREE ZONES AND TYPES 

Among the smaller parks Estes Park shows a typical zonal arrange- 
ment of the tree species of northern Colorado. There are three well- 
defined forest types: (i) the yellow pine type, developed typically 
as an open woodland which reaches from the upper foothills to an 
altitude of 9000 feet; it occupies the ridges and slopes of the lower 
part of the park, but at higher elevations occurs only in the open 
valleys. In the open it occurs on small rocky knolls and ridges, whence 
it invades the grasslands of the park floor. (2) The lodgepole pine- 
Douglas spruce type occurs above the yellow pine type between 8000 feet 
and 10,000 feet, though below the lesser altitude the growth is mixed 
to some extent with the yellow pine, while above the greater altitude it 
is mixed with Engelmann spruce. (3) The Engelmann spruce-alpine fir 
type constitutes the forest at timber line and usually some distance 
below it. Timber line is here at 10,500 feet. From 8500 to 9000 feet 
the grass land of Estes Park is in the form of typical mountain 
meadows.^ 

Among the larger parks San Luis exhibits a rather typical distribu- 
tion of vegetation. On the high mountain sides flanking San Luis 
Valley are pine, aspen, and spruce. Lower down are pinon and cedar; 
in the valleys and along the streams are cottonwood and willovsr. Away 
from the streams and on the arid basin floor greasewood is the principal 
growth. 2 

1 F. E. Clements, The Life History of Lodgepole Pine Forests, Bull. U. S. Forest Service 
No. 79, 1910, pp. 7-8. 

- C. E. Siebenthal, Geology and Water Resources of the San Luis Valley, Col., Water- 
Supply Paper U. S. Geol. Surv. No. 240, 1910, p. 26. 



CHAPTER XXI 

TRANS-PECOS HIGHLANDS 

Mountains and Basins 

The Trans-Pecos region embraces an assemblage of topographic 
forms which individually resemble the features of adjacent provinces, 
the Rocky Mountain province on the north, the Arizona Highlands 
province on the west, and the Mexican plateau on the south, and it 
may therefore be regarded as a transition province. The Trans-Pecos 
ranges do not have that continuity which marks the main mountain 
ranges of the Pacific Cordillera. They exhibit a great variety of slopes 
produced at different geologic times and in many different ways; the 
province includes a mixed group of topographic forms not conveniently 
classified with the forms of adjoining provinces. In this respect it is 
unlike the other physiographic regions of the United States, each of 
which has a certain essential unity of structure or topography or both. 

Mountains and intermontane plains of several types and of variable 
extent are the predominating features of the Trans-Pecos country. The 
latter are in part plains of degradation, in part broad constructional 
plains built up by detritus from the bordering mountains and called 
bolsons (Spanish holson, for "large purse"). The trend of the moun- 
tains and intervening basins is north-south, except near and south of 
the New Mexico-Texas boundary where they trend northwest-southeast. 
In general the elevations are distinctly lower than those of any other 
portion of the Pacific Cordillera in this longitude. Only two peaks rise 
above 8000 feet and the general elevation of the lowlands is from 3500 
to 4500 feet. 

While the greater number of the Trans-Pecos mountains have a fault- 
block origin, as a whole they are of diverse origin, structure, and topog- 
raphy. They exhibit many irregular forms of relief and all have sharp 
and rugged outlines. Few of them rise to the height of the dry timber 
line (6000 feet). On the summits and in the higher canyons of the 
Sacramento, Chisos, and Davis mountains, and a few others, this ele- 
vation is exceeded and a certain amount of timber is found. On the 
lower and drier mountains the vegetation consists of edible pines, a 
variety of junipers, and several species of maguey. The lower eleva- 

387 



S88 



FOREST PHYSIOGRAPHY 




25 50 



Fig. 133. — Principal mountain ranges of the Trans-Pecos province, chief drainage features, and the 
bordering Llano Estacado on the east. (U. S. Geol. Surv.) 



TRANS-^PECOS HIGHLANDS 389 

tion of the group as a whole is expressed in the lesser rainfall and 
general barrenness of the mountains in contrast to the partly timbered 
Rocky Mountains to the north. The highest summit is Sierra Blanca 
(ii,SSo feet) in the Sacramento range in southern New Mexico, but in 
general the peaks fall short of this altitude. 

Mountain Types 

Four types of mountains may be identified : (i) mountains of deforma- 
tion, consisting of structural folds or tilted fault blocks in which the 
outline of the mountain is in sympathy with the structural breaks or 





-~^' 






Fig. 134. — Western face of the Fra Cristobal Mountains, New Mexico. Two faults, a and b, give prom- 
inence to the mountain front. They are represented in the section below the photograph. (Lee 
and Girty, U. S. Geol. Surv.) 

deformations, for example the Sandia and Manzano mountains east of 
Albuquerque; (2) plateau mountains, consisting of nearly horizontal 
plateaus without important deformations. This type of mountain 
occurs in the form of summits or shoulders and in close proximity to 



39° FOREST PHYSIOGRAPHY 

the higher rehef features of the province.^ (3) Mountains due to the 
upthrust of a granitic core through sedimentary rock that now forms the 
borders of the range, as the Black and Mimbres ranges. (4) Moun- 
tains consisting chiefly of volcanic material like San Mateo -and Valles 



Fig. 135- — East-west section across the Trans-Pecos Highlands north of El Paso, Texas. pC, pre-Cambrian 
quartzite and porphyry; COS, Ch, gs, etc., paleozoic limestone, sandstone and gypsum; K, cretaceous 
limestone and sandstone; gr, intrusive granite; Qb, Quaternary basin deposits. Scale, i inch repre- 
sents nearly so miles. (Richardson, U. S. Geo!. Surv.) 

mountains and others. The members of the last-named group fall into 
three subtypes: (c) old igneous vents such as dikes and necks, (b) vol- 
canic craters, and (c) mesas capped by sheets of lava that have pro- 
tected the underlying rocks from the denudation that carried away the 
surrounding material. 

The Trans-Pecos province is one of the least-known physiographic 
provinces in the United States and few generalizations may be made 
concerning details of mountain form beyond those in the preceding 
paragraph. It is known that the province as a whole is separated from 
the Rocky Mountains province at Bernal, New Mexico, by a broad 
level plain or plateau, and it is not until about 100 miles south of Bernal 
that the mountains of the Trans-Pecos begin in the Jicarillas, the north- 
ern outliers of a chain of mountains, the loftiest ranges of the province, 
that extends with marked continuity through New Mexico and Texas 
as far as the 3 2d parallel. The individual members of the chain are 
the Jicarillas on the north, and next in order from north to south are 
the Sierra Blanca, Sacramento, Sierra Guadalupe, Comanches, Caballos, 
and the Sierra de Santiago. These constitute the front .ranges of the 
province and they give a distinctive character to the eastern edge of the 
highland belt in which they lie. The rocks composing these mountains 
are chiefly limestone and sandstone. The general structure of the east- 
ern border ranges is an eastward-dipping monocline ending at the Rio 
Pecos, but there are many lateral ridges and separate peaks. On the 
west the mountains of the eastern border terminate in a steep scarp 
1000 to 2000 feet high. The long eastern slopes correspond with the 
dip of the underlying strata. 

West of the front ranges of the Trans-Pecos country are other ranges 
of the fault-block type. They occur as short sierras or groups of sierras 
in the form of isolated mountains or elongated chains surrounded by 
extensive and nearly level desert plains. They have lower altitudes 

I R. T. Hill, Physical Geography of the Texas Region, FoHo U. S. Geol. Surv. No. 3, 1900, p. 3. 



TRANS-PECOS HIGHLANDS 



391 



than the front ranges, and so isolated are the various members that no 
group name has been given them. The principal ranges are, however, 
arranged in two lines on either side of the Rio Grande Valley. On the 
east side are the Sandia, Manzano, Oscura, San Andreas, and Organ 
ranges; on the west are the Nacimiento, Limitar, Magdalena, Cristobal, 




Fig. 136. — Fault -block mountain in the Trans-Pecos Highlands, Texas. 
(Marfa quadrangle, U. S. Geol. Surv.) 

Caballos, and Cuchillo Negro ranges. The fault scarps of these ranges 
are always steep and in general face inward toward the Rio Grande 
Valley, which is thus a great structural depression or series of elongate 
basins, though there are some important exceptions to this rule. They 
are all high and in process of vigorous dissection, and hence display a 



392 



FOREST PHYSIOGRAPHY 



varied relief. The trend of the group is, however, definite, due to their 
fault-block origin, and of similar definiteness are the valleys that occur 
among them. Westward of these block mountains are many short 
independent blocks surrounded by bolson deserts and not capable of 
union into related chains. They rise from desert plains and in general 




^'/f^ 



Fig- 137- 



■ Western escarpment of the Caballos Mountains, New Mexico, and the dissected alluvial 
slope at their base. (Lee, U. S. Geol. Surv.) 



have steeper descents on their western than on their eastern sides. They 
consist for the most part of fault blocks with monoclinal dips, although 
in places extensive folded structures also occur. 



FRANKLIN RANGE 

The most detailed study of mountain form and structure in the 
Trans-Pecos region is by Richardson, whose structural sections of the 
Franklin range are shown in Fig. 138. They will serve as illustrations 
of a type of mountain found in the province. The Franklin range is a 
long, narrow, crust block resembling the mountains of the basin-range 
type in its general features but differing from many though not from 
all of them in having a more complex system of internal faults. The 
strata strike parallel to the trend of the range and dip westward at 
steep angles. On the steeper eastern face of the Franklin range are 



TRANS-PECOS HIGHLANDS 



393 



exposed the eroded edges of the strata composing the fault block, while 
the gentler westward slope coincides to an important degree with the 
dip of the underlying strata. The range is broken into several second- 
ary blocks by normal parallel faults some of which strike with the 
trend of the range, but there are also several transverse fractures, and 
the strike of a few of the faults is a curve. Both the eastern and the 
western margins of the range are marked by faults; that on the western 
border consists of two parallel faults at the base of the range between 
the foothills and the main mountain mass. The greatest displacement 
is in the central part of the range, where a throw of 2500 feet has been 
determined. 




Fig. 138. — Section across Franklin Mountains, showing relation of structure to relief. In, quartzite; 
rhp, rhyolite porphyry; Cb, sandstone; Gep, Cm, Sf, Ch, and Kcm, limestone; gr, intrusive granite; 
Tap, andesite porphyry; Qb, basin deposits. Scale i inch represents 2 miles. (Richardson, U. S. 
Geol. Surv.) 




Fig. 139. — East -west section across the Franklin Mountains north of El Paso, Te.xas. To supplement 
Fig. 138. Legend and scale as in Fig. 138. 

The fault at the eastern foot of the range is completely concealed by wash and its position 
is hypothetical. That the mountain front is the locus of a fault is suggested by the evidences 
of geologically late (probably Quaternary) faulting at El Paso, where displacements in allu- 
vial deposits may be seen, and by the benches west and northwest of Fort Bliss at eleva- 
tions ranging about 4000 feet. The benches are the upper portions of broken alluvial slopes 
which in places fringe the base of the range in an uneven eastward-facing scarp varying from 
10 to so feet in height. In many places the bench has been destroyed by erosion along the 
many arroyos that descend from the adjacent mountains. The original fault along the base of 
the range is probably of ancient origin, for the drainage has diversified the eastern border and 
to a large extent obliterated that inequality of slopes that obtains in the case of a young block 
mountain.i 



VOLCANIC MOUNTAINS AND PLATEAUS " 

In addition to the mountains formed out of tilted crust blocks of sed- 
imentary material there are many eccentric and irregular mountains of 
volcanic origin that rise from broad plains. Of this type are the Chisos 
(ghosts), Corazones (hearts), the Sierra Blanca, and the Davis moun- 
tains, among which the last-named are the most extensive. They con- 
sist of a group of volcanic necks and dissected volcanic plateaus that end 

1 G. B. Richardson, El Paso Folio U. S. Geol. Surv. No. 166, 1909. 

2 R. T. Hill, Physical Geography of Texas, Folio U. S. Geol. Surv. No. 3, igoo. 



394 



FOREST PHYSIOGRAPHY 




-d to 




TRANS-PECOS HIGHLANDS 395 

at the south in a great escarpment over 1000 feet in height that over- 
looks the continuation of a broad intermontane plain toward the south. 

The mesa and cuesta types of mountains are capped in some in- 
stances with old igneous material in places 500 feet thick. The volcanic 
caps are remnants of former sheets of similar material that have been 
all but removed by denudation. Elephant Cuesta and Nine Point 
Mesa are illustrations of this kind of mountain. Besides these are 
other volcanic mountains of recent origin, cinder cones or true volcanic 
craters accompanied by sheets of lava which flowed from them. The 
craters are of interest because they are the most easterly known in the 
United States and the only ones lying east of the front of the Cordillera. 
The cinder cones have been formed since the degradation of the Mesa 
de Maya and Ocate plateaus, for they rise out of the newer and lower 
plain below the latter. The most conspicuous crater is Mount Capu- 
lin, a very symmetrical cinder cone with a vast crater at the top of it. 

Within the Trans-Pecos Highlands are extensive areas of uplands 
with sublevel summits bordered more or less completely by pronounced 
escarpments. They occur as large benches that border the mountain 
ranges or that rise from the bolson deserts. They are either com- 
pletely isolated from the mountains or project bench-like from the 
bases of the mountains. They are lava-capped mesas whose summit 
layers of hard volcanic rock have protected the more friable material 
underneath them; they are distinguished from the flat-topped mountains 
noted above only by their greater extent and lesser elevation. They 
are cut by deep canyons, bordered by steep escarpments, and owe their 
present outlines to marginal erosion. Northeastern New Mexico, Fig. 133 , 
is therefore not a part of the Great Plains but an eroded plateau of 
Cretaceous rock surmounted by basaltic flows. ^ 

Red Beds MESA DE MAYA 

Dakota Sandstone 
Colorado Shale 



& 


Laramie Shale 


Basalt 


Basalt 


Rasalt 








Srs::^^ 


=^== 


IIZ^^ 



LENGTH OF SECT!ON=100 MILES 
HEIGHT OF SECTION = 2 MILES 

Fig. 141. — Upturned strata on the eastern border of the Rockies, the anticlinal structure of the bordering 
strata underneath the Mesa de Maya, and the protective influence of the basalt cover. (After Keyes.) 

The three most conspicuous plateau plains of northern New Mexico 
are known as the Mesa de Maya, the Ocate Mesa, and the Las Vegas 

1 R. T. Hill, Notes on the Texas-New Mexico Region, Bull. Geol. Soc. Am., vol. 13, 1892,, 
pp. 85-100. 



396 



FOREST PHYSIOGRAPHY 



Mesa. The western portion of Mesa de Maya is also known as Raton 
Mesa or Raton Mountains. The mesa is a long dissected plateau almost 
due east of Trinidad, Colorado, which extends southward into New 
Mexico and Texas. Its border rises nearly 4^00 feet above- the adja- 
cent valleys and the massive summit is composed of thick beds of old 
lava now dissected into remnants of a once more extensive plateau. 
Underneath the lava are less resistant sandstones and shales (Upper 
Cretaceous) . 

Raton Mesa is 8 miles long, 4 miles wide, and includes about 20 square 
miles. It has been entirely separated by erosion from a similar area 




Fig. 142. — Topography of Mesa de Maya, south-central Colorado. Typical lava-capped mesa with 
steep bordering scarps and Flattish summit. (U. S. Geol. Surv.) 

to the south and from the main lava field to the east. The aggregate 
thickness of the basalt flows which constitute the cap rock of Raton 
Mesa and of the Mesa de Maya is from 250 to 300 feet about their 
borders, and increases to 500 feet toward the central part of the western 
mesa. At least 8 distinct beds of lava have been identified, which prob- 
ably represent the same number of independent eruptions. The differ- 



TRANS-^PECOS HIGHLANDS 397 

ent beds are 30 or more feet in thickness, though they vary greatly from 
place to place. ^ Raton Mesa has a mean elevation of about 1800 feet 
and is bordered by an almost vertical escarpment from 200 to 300 feet 
high, an escarpment so sheer as to render it almost inaccessible, Fig. 141. 

There is a dense growth of pihon and juniper along the base of 
the Raton Mesa; the small streams that head in the plateau are 
fringed with cottonwoods; on the steep border of the plateau, pine and 
spruce trees are scattered through a dense undergrowth of scrub oak, 
with aspen appearing locally near the base of the escarpment. The 
entire district up to 7500 feet affords a scanty growth of nutritious 
grasses well suited for sheep farming, which is one of the chief indus- 
tries. The tableland on the summit of the mesa supports a growth of 
bunch grass. ^ 

The Ocate Mesa has a cap rock of thick sandstone and it is the rem- 
nant of a lower-lying mesa that extends westward to the foothills of 
the Rocky Mountains between the Arkansas River in Colorado and the 
Cimarron River in New Mexico. The largest development of the Ocate 
Mesa is between the Cimarron Valley and the Mora, where from a 
broad platform rises Ocate crater (8900 feet). The eastern border of 
Ocate Mesa is an escarpment nearly 500 feet above the plain to the 
east, known as the Las Vegas Mesa, which extends south of Mesa de 
Maya to the great cliffs of the Canadian valley and east toward the 
Great Plains near the Texas line. The surface of Las Vegas Mesa 
slopes gently to the east; the western border has an average altitude 
of about 8600 feet. It is a vast stratum plain underlain by a chalky 
sandstone (Colorado formation). Many volcanic craters and dikes rise 
out of it to diversify and complicate its relief. 

The cliffs which terminate the eastern border of Las Vegas Mesa form one of the longest 
and most remarkable escarpments in America. They are continuous with the cliffs of Galistes 
Mesa and extend in an indirect manner from the 104th meridian southwest to the io6th 
meridian, or nearly 300 miles. The cliffs are developed upon sandstone and overlook the 
deep Pecos Valley. 

Drainage Features 

A detailed map of New Mexico and western Texas, Fig. 142, displays 
many features characteristic of surface drainage in arid lands. A large 
number of enclosed basins of structural origin occur, and these are in the 
main floored with loose sediments derived from the surrounding moim- 
tains. About the margins of the basins are long talus slopes, huge 
bowlder and alluvial fans, and dry arroyos. The basins are without 

1 R. C. Hills, Elmoro Folio, U. S. Geol. Surv. No. 58, 1899, p. 3, col. 2. 
8 Idem, p. I, col. i. 



398 FOREST PHYSIOGRAPHY 

surface streams of any extent, a few watercourses entering them from 
surrounding highlands, but the porous nature of the soil, the high rate 
of evaporation, and the low rainfall, cause the streams to disappear before 
they have traveled far from the margins of the basins. The annual 
rainfall is in some places less than lo inches, over the greater part of the 
region it does not exceed 15 inches, and everywhere it is chiefly in the 
form of summer thunder showers of short duration and limited extent. 

All of the basins or bolsons, as they are sometimes called, are charac- 
terized by "lost rivers,"— streams that disappear about the borders of 
the basins. The floors of some of the basins are occupied by salt marshes 
or temporary lakes. In the largest basins, those between the Sierra 
Madre and Guadalupe mountains, the salt deposits are of great extent 
and have been used for hundreds of years by the Mexican population 
as one source of a salt supply. Around the margins of some of the 
bolsons are benches consisting of fan-shaped heaps of land waste de- 
rived from the mountains and deposited by torrential streams. 

The word "bolson" is of Spanish origin and according to Hill it designates structural 
valleys between mountains or plateau plains which have been partially filled with debris from 
adjacent eminences.^ Bolson originally meant a constructional plain bordered by mountains 
or plateau escarpments that supplied the material with which the bolson is floored; the term 
did not cover the bordering mountains, though the definition implied that the bordering moun- 
tains are features normally associated with the plain, and that a bolson plain was part of an 
interior basin.2 In short, a bolson plain is the floor of an interior basin with such variations 
in its expression as are naturally associated with variations in climate, disposition of waste, 
size of basin, length of existence, etc. 

The basin floors are characteristically flat and in broad view are 
somewhat similar in appearance to the plateau plains just described. 
They are, however, to be distinguished from the plateau plains by the 
fact that they are, at least in part, surfaces of aggradation, while the 
plateau plains are on the whole either destructional surfaces or surfaces 
that have been at least partly preserved from destruction by a cap of 
resistant lava. 

Longitudinal Basins 
The basins of the Trans-Pecos region occur in four longitudinal belts 
in sympathy with the belted arrangement of the intervening mountains, 
Fig. 133. The easternmost lies along the eastern fronts of the Guada- 
lupe and Santiago ranges. The second belt lies between these ranges 
and the Sierra Diablo and Cornudas mountains. The third line of 
basins lies between the Sacramento and Sierra Blanca mountains on 
the east and the Sierra Oscura and San Andreas ranges on the west. 

1 R. T. Hill, The Physical Geography of the Texas Region, Folio U. S. Geol. Surv. No. 3, 
1900. 

' W. G. Tight, Am. Geol., vol. 36, 1905, pp. 271-284. 



TRANS-PECOS HIGHLANDS 399 

The fourth line lies between the last-named mountains and the Sierra 
de los Caballos on the borders of the Rio Grande. 

Among these four longitudinal basins the Hueco basin, Fig. 133, is the 
largest. It lies partly in New Mexico, partly in Texas, is about 200 
miles long, about 25 miles wide, and stands about 4000 feet above the 
sea. The mountains that border and enclose it are 2000 to 5000 feet 
higher. A few miles north of the New Mexico-Texas boundary the basin 
is crossed from west to east by a low divide. The southern half is drained 
by the Rio Grande; the northern half is a closed basin with salt marshes 
and unusually interesting dunes of white gypsiferous sands, a district 
known as the Tularosa Desert. In the vicinity of El Paso the Hueco 
basin is a structural basin or trough deeply filled with detritus. The 
streams wither at the foot of the mountains, and the mouths of the 
mountain arroyos are marked by huge detrital cones and fans that 
spread radially outward and finally coalesce with the wash from the 
intervening slopes. 

JORNADO DEL MUERTO 

The most noted basin of the Rio Grande Valley is the Jornado del 
Muerto Bolson. Its name means "the journey of death" and was 
given to it in pioneer days because of the great difiScuity then involved 
in crossing its dry, barren, and inhospitable wastes. 

The Jornado basin lies in south-central New Mexico. It extends 
north and south a distance of more than 200 miles, and is from 30 to 
40 miles wide. It is a flat-bottomed basin except along the Rio Grande 
where the river has cut a valley 400 feet below the general level. Its 
margins are upturned steeply on all sides to heights of 2000 and 3000 
feet above the general level. In the central part of the basin are a 
number of shallow depressions which hold storm waters that some- 
times linger as lakes for several months, seldom through the year. At 
various points the even surface of the basin floor is broken by low hills 
of volcanic origin, among which may be mentioned the Dona Ana Hills, 
San Diego Mountains, and Cerro Roblero in the southern part of the 
basin. All of the volcanic cones are of recent origin and some of them 
have perfectly preserved craters. From some of the cones basalt 
flows have extended out over the surrounding plain, the one south of 
San Marcial covering more than 100 square miles. 

It has been shown recently 1 that certain interior basins of the Trans-Pecos country, among 
them the Jornado del Muerto, instead of being structural valleys deeply floored by mountain 
waste, have a rock surface developed on the beveled edges of the strata, representing a total 

1 C. R. Keyes, Rock Floor of Intermont Plains of the Arid Regions, Bull. Geol. Soc. Am., 
vol. ig, 1908, pp. 63-92. 



400 



FOREST PHYSIOGRAPHY 



thickness of thousands of feet, and that for the most part the rock floors of these plains are 
covered by a thin veneer of detritus only instead of the thick alluvium usually ascribed to 
them. Rarely does the thickness of the detrital mantle exceed loo feet. The general slope 
of the Jornado del Muerto plain for example is only 2° or 3°, while the dips of the strata are 
in many cases as high as 30° in the same direction, and even vertical. On the beveled edges 
of these steeply inclined beds alluvium and also broad sheets of basaltic lavas have been 
laid down. 

BASINS OF THE RIO GRANDE VALLEY 

Among the most important basins of the Trans-Pecos country are 
those drained by the Rio Grande. This river from the San Luis 
Valley in southern Colorado to the point where it cuts the easternmost 
mountains of the province (long. 103° W.) flows almost continuously 




Fig. 143. — Valley of Rio Grande, El Paso, Texas, showing passage of the river from the Mesilla Valley 
to the Hueco basin across the southern end of the Franklin range. Note the terraced margins of 
the dissected basins. (Hill, U. S. Geol. Surv.) 

through a series of old structural basins connected by canyons that 
increase in length and depth toward the southeast. The present course 
of the Rio Grande is owing in part to the basin feature and in part 
to volcanic action, and the activities of the river itself. 

Long after the partial filling of the broad structural troughs of the region there was an early 
period of valley cutting which was followed by a second period of valley filling, probably on 
account of changed topographic and climatic conditions. Near the close of the second period of 
aggradation great sheets of basalt were extruded. During this time the stream courses were in 
many instances violently changed and the Rio Grande, which formerly ran southward through 
the Jornado del Muerto basin into the interior basins of northern Mexico, was diverted into 
Engle and Las Palomas valleys, which are much narrower than the first-named basins. At 
the same time topographic changes due to volcanic action farther south probably forced the 
Rio Grande eastward to its present course south of the Franklin range at Hill Pass and south- 
eastward to the Gulf. The volcanic eruptions and changes of river courses were followed by 



TRANS-PECOS HIGHLANDS 401 

a second period of erosion in which were formed the present narrow elongated valleys that 
stand at an elevation several hundred feet lower than the basins in which they were cut. A last 
phase of river activity is expressed in the form of silt accumulations on the floors of the flood 
plains, a filling with a maximum depth of 85 feet in the El Paso canyon. The river is carrying 
an immense quantity of silt to-day; on the average it transports about 14,580 acre feet of 
mud a year.' 

The flood plain of the Rio Grande is cut well below the level of the 
Jornado del Muerto and is known in part as the Mesilla Valley. This 
division is about 45 miles long and 5 miles wide. Along the valley mar- 
gins terraces of notable extent and height have been formed. Some of 
them are of structural origin; their upper surfaces correspond with the 
dip of the rock in many instances, and rock outcrops along their valley- 
ward margin. At a lower level are alluvial terraces representing com- 
plexities in the down-cutting of the Rio Grande since gaining its present 
course across the basins. 

The Rio Grande is a storm-water stream subject to great and sudden 
floods. The rainfall occurs principally in the form of violent showers or 
cloud-bursts which fill the dry stream beds with turbulent floods of short 
duration. When such floods occur simultaneously at many points they 
are likely to cause destructive floods on the valley floor where the fertile 
irrigable lands are located and where most of the population and the 
principal towns are to be found. 

Climate, Soil, and Vegetation 

The rainfall of New Mexico varies from 20 to 25 inches in the moun- 
tains, as above Las Vegas and Cloudcroft, to about 15 inches on the 
Great Plains to the east in the vicinity of Roswell and Carlsbad, so 
that the Pecos River, forming the eastern boundary of the Trans-Pecos 
Highlands, receives practically no tributaries from the east. The 
effects of the small rainfall of lower elevations are reenforced by the 
porous nature of the soil, upon which there is no extensive surface 
drainage; the water also drains rapidly away underground in many 
places through fissured limestone rock.- At El Paso the mean annual 
precipitation is 9.85 inches, ranging between a maximum of 18.30 inches 
in 1884 and a minimum of 2.22 inches in 1891. The average humidity 
is 38.8 %, ranging between 23.2 % in May and 47.3 % in January.^ The 
mean annual precipitation throughout western Texas is about 12 inches. 
It falls mainly in the summer months in the form of brief showers and 
is variable and uncertain. 

1 W. T. Lee, Water-Supply Paper U. S. Geol. Surv. No. 188, 1907, pp. 20^24. 

2 Freeman, Lamb, and Bolster, Surface Water Supply of the United States, 1907-08, pt. 8, 
Western Gulf of Mexico, Water-Supply Paper U. S. Geol. Surv. No. 248, 1910, p. 114. 

' G. B. Richardson, El Paso Folio U. S. Geol. Surv. No. 166, 1909, p. 2. 



402 



FOREST PHYSIOGRAPHY 



In the lower Pecos Valley irrigation has reached a very high stage of development.^ Thou- 
sands of acres are under cultivation, beginning a short distance above Roswell and continuing 
into Texas; below this fertile belt but little irrigation is carried on because the seepage water 
contains a large amount of alkali, which renders it unfit for irrigation purposes. 

The floors of the arid basins in the Trans-Pecos region generally con- 
sist of fine detrital material and support a growth of stunted shrubs and 
grasses, such as mesquite, greasewood, and cactus. Along the river 
bottoms are cottonwoods and an undergrowth of shrubs. The coarser 
talus slopes are covered with a growth of yucca, cactus, and other 
desert flora and a scattered scrubby growth of oak, cedar, and juniper. 
These forms are gnarled and stunted at lower elevations, but in higher 





Fig. 144. — North end of San Mateo Mountains, Trans-Pecos Highlands \l« NUmlo. Shows char- 
acteristic tree-covered slopes. Mountains composed of rhyolite flows and tuffs. (Gordon, U. S. 
Geol. Surv.) 

situations they become increasingly more exuberant in growth." Upon 
the slopes and summits of the highest mountains, the Chisos, Davis, 
Capitan, and Sacramento ranges, a thrifty tree growth of pine and fir 
is found; upon the lower mountains the tree growth becomes more 
scattered and upon the lowest ranges no true forests appear. The 
Black range bears a good growth of pine upon its upper slopes; the 
Magdalena range and San Mateo Mountains have poorer growths of 

1 G. B. Richardson, El Paso Folio U. S. Geol. Surv. No. 166, 1909, p. 115. 

2 C. E. Dutton, 6th Ann. Rapt. U. S. Geol. Surv., 1885, p. 125. 



TRANS-^ECOS HIGHLANDS 



403 




Cuntour inlerval lOOO feet 

I T Timberless, Grazing EIZl Woodland ^ Less than 2000 feet B.M. 

1 1 2000 to 5000 feet B.JI. ■■ 5000 to 25,000 feet B.JI. 
Fig. 145A. — Timber belts, Capitan Mountains, New Mexico. Note (ij the manner in which the timber 
belts follow the waterways, (2) the increase in growth with increase of elevation, and (3) the island- 
like outlines of the densest growths. (Adapted from U. S. Geol. Surv.) 

pine interspersed with cedar and juniper, though in the better-favored 
situations good stands are found. ^ 

The ranges of the species of trees occurring in the Trans-Pecos region 
vary as to rainfall, soil, and slope exposure. The lowest and best growth 
is found on the northern cooler and moister slopes and wherever the best 
soils have been developed. Except on the broader summits the soil 
has little humus for the undergrowth is scattered and light, oxidation 
of decaying vegetation is rapid and fairly complete, and erosion is in 
general active. There is a notable banding of the various species of 
forest trees, though the ranges of the different species overlap, as shown 
in Fig. 145B, which illustrates distributions in the Lincoln Forest Reserve 
of New Mexico (Capitan and Sierra Blanca ranges). The highest, or 
subalpine zone is found in this district between 9000 and 11,000 feet. 
Engelmann spruce is the principal tree of this zone with subordinate 
amounts of white fir, red fir, Mexican white pine, and aspen, generally 
in groves. The yellow pine zone between 6400 and 9000 feet includes, 
beside the dominant yellow pine, red fir, white fir, Mexican white pine, 
and oak. Between 5000 and 6400 feet is the woodland zone in which 
the principal species are pinon, juniper, cedar, scrub oak, and, along the 
streams, ash, box elder, and walnut. 

The Trans-Pecos forests seldom form dense stands; open scattered 
forest growth is the prevailing type. Since the forests grow only at the 
higher elevations, they are in relatively inaccessible situations, for the 
settlements are found in the valleys. The principal value of the forests 

1 Lindgren, Groton, and Gordon, The Ore Deposits of New Mexico, Prof. Paper U. S. 
Geol. Surv. No. 68, 1910, p. 217. 



404 



FOREST PHYSIOGRAPHY 



is in relation to water conservation. Many small perpetual streams are 
limited to the forested zone; only a few advance even two or three 
miles into the bordering deserts. Forage grasses form a ground cover 
of great extent both in the parks of the forested zone and below the 




NARROWLEAF 



COTTONWOOD 




MEXICAN V HITE PINE 




engelmaSn spruce 



WOODLAND 
ZONE 



Y 

YELLOW PINE 
ZONE 



SUBALPINE 
ZONE 



Fig. I4SB. — Range and development of tree species in Lincoln National Forest, Trans-Pecos province. 

(U. S. Gaol. Surv.) 

7000 foot level where the forest ends. In the more accessible situations 
these have been irreparably damaged by overgrazing, for with the de- 
struction of the grasses deep and extensive erosion has taken place and 
rich pastures have been laid waste. ^ 

» Plummer and Gowsell, Forest Conditions in the Lincoln Forest Reserve, New Mexico, 
Prof. Paper U. S. Geol. Surv. No. 33, 1904, pp. 10, 11, 18. 



CHAPTER XXII 

GREAT PLAINS 
TOPOGliAPHY AND STRUCTURE 

The Great Plains province slopes eastward from the foot of the 
Rocky Mountains to the valley of the Mississippi, where it merges into 
the Prairie Plains on the north and the Coastal Plains on the south. 
The Great Plains appear as wide areas of relatively flat tabular sur- 
faces crossed by broad shallow valleys drained by scores of eastward- 
flowing streams tributary to the Mississippi. Certain portions, as in 
central Montana, are drained by streams sunk in narrow canyons 
several hundred feet deep. The general expanse of smooth surface 
is also broken in some places by buttes, mesas, domal uplifts, extended 
escarpments, and local areas of "badlands." In some districts ex- 
tensive areas are covered with sand hills, as in northwestern Nebraska, 
where is found a typical area of this character several thousand square 
miles in extent. 

As a whole, the province descends toward the east about lo feet per 
mile and from altitudes of about 6.000 feet on the west to about 1000 feet 
on the east, though the elevations and the general regional slope have 
considerable variation from place to place. An important illustration of 
variation in altitude is Pine Ridge, an irregular escarpment which extends 
from the northern end of the Laramie Mountains in Wyoming eastward 
to the northwestern corner of Nebraska and the southern part of South 
Dakota. It marks the northern boundary of the higher portions of 
the Great Plains, and from it clilfs and steep slopes descend northward 
1000 feet into the basin of the Cheyenne River. North of the Cheyenne 
River the divides are much lower and the surface as a whole does not 
attain the level of the High Plains to the south. 

The plains topography is developed on a great mass of (i) rather 
soft deposits — sands, clays, and loams — spread out in the form of thin 
and extensive beds that slope gently eastward and (2) gently inclined 
and more indurated stratified rock varying from limestone and gypsum 
through shale and sandstone to conglomerate. The material of the 
first class is found chiefly in that subdivision of the Great Plains called 
the High Plains which extend from the southern margin of the bad- 

405 



4o6 



FOREST PHYSIOGRAPHY 



lands to the parallel of 32° south in central- western Texas, and east 
and west extends between the looth and 104th meridians. The hard 
rock elsewhere underlying the Great Plains is for the most part thinly 
cloaked with rock waste, and its topography is in large part -responsive 
to structure save (a) where the effects of base-leveling are still topo- 
graphically expressed or (b) where glaciation has modified the surface 
or (c) where local alluviation has concealed an earlier structural surface. 
The two classes of material forming the Great Plains were derived 



-t 2 I ' 4 

I" 
— 4. 



^%r 







4 '' 



II ' 



Fig. 146. — Geologic map of the Texas regions, showing the relations of the Great Plains formations to 
tliose of the surrounding provinces, i, Older granite; 2, Paleozic and Mesozoic; 3, Cambrian-Silurian; 
4, Carboniferous; 5, Permian; 6, Jurassic; 7, Lower Cretaceous; 8, Upper Cretaceous; 9, Nonmarine 
Tertiary; 10, Marine Eocene; 11, Coast Neocene; 12, Later igneous. (Hill, U. S. Geol. Surv.) 

mainly from the west and deposited in stratified condition upon flood 
plains and lake floors and in part on the sea floor. The region has 
suffered broad uplift and depression a number of times in its geologic 
history, but these deformations have been regional in character and 
have not deformed the sedimentary series in a complex manner except 
in local instances.^ 



1 Darton and Salisbury, Cloud Peak-Fort McKinney Folio U. S. Geol. Surv. No. 142, 
06, p. 2, col. I. 



GREAT PLAINS 



407 



H 



1 1 



5 ■■-■I 



i \ 



408 FOREST PHYSIOGRAPHY 

Although the strata of the plains lie sensibly flat within short dis- 
tances, the structure of the hard rock, as shown in Fig. 147, has the 
general character of a great geosyncline which rises on approach to the 
eastern border of the Rocky Mountains, where the steeply inclined, 
eastward-dipping strata appear in the form of hogback ridges, fringing 
the front ranges of the Rockies. This regional westward dip of the 
Great Plains strata is distinctly characteristic ; but the general structure 
is modified in places by structural deformations of a certain degree of 
importance. In southeastern Colorado, for example, there is an arch 
in the form of an anticline which extends southeastward from the Green- 
horn and Wet Mountain ranges and passes under the Mesa de Maya, 
Fig. 141. Again, the continuity of the monocline of the foothills on the 
western border of the Great Plains, formed upon the upturned edge 
of the Plains strata, is broken by a number of small offsets, a series of 
three occurring at Greeley, Colorado, Fig. 117.^- 

Over the larger portion of the Great Plains the westward-dipping 
strata end in long, low, ragged, eastward-facing escarpments; the topog- 
raphy thus has a "stair step" composition, the escarpments stand out 
as conspicuous risers and the broad, flat, inter-escarpment areas rep- 
resent the treads. Of such origin are the Flint Hills, the Dakota 
Sandstone Hills, and the gypsum hills of Kansas and Nebraska; and 
similar examples occur in many other places. These features are most 
prominently developed where the hard strata (sandstones) are thick 
and the soft strata (shales) thin. Where the reverse is true the escarp- 
ments may be so low as scarcely to be identifiable and the inter-escarp- 
ment tracts dissected by a maze of branching systemless streams. For 
example, the Pierre shale occupies many thousand square miles of 
country adjoining the Black Hills and gives rise to a monotonous 
landscape of rounded hills thickly covered with grass instead of the 
more common tabular relief bordered by escarpments.^ The Great 
Plains of Texas are developed largely upon an extensive limestone 
stratum (Edwards) which is completely surrounded by escarpments 
of erosion. In the Llano Estacado, which is the southern end of the 
High Plains subdivision, the surface is for the most part capped by 
alluvium from the mountains.^ 

1 N. H. Darton, Geology and Underground Water Resources, Central Great Plains, Prof. 
Paper U. S. Geol. Surv. No. 32, 1905, pp. 74-75. 

' Idem, pp. 22-23. 

3 R. T. Hill, Physical Geography of the Texas Region, Folio U. S. Geol. Surv. No. 3, 1900, 
pp. 6-7. 



GREAT PLAINS 409 

Stream Types 

Two types of streams cross the Great Plains, (i) streams whose head- 
waters are in the mountains and (2) streams whose headwaters are on 
the plains. Those streams whose headwaters are in the mountains are 
supplied with water more or less regularly either through rain or snow 
or both. In addition, their headwaters often drain glacial lakes and 
these tend to regulate the flow. The result of the somewhat regular 
water supply is that although the streams may become very low and 
even dry up occasionally, they are for the most part through-flowing 
the entire year. This result appears the more striking when it is known 
that their plains tributaries are intermittent and feeble and that the 
master streams suffer heavy losses by evaporation in crossing the semi- 
arid plains country. 

A stream of this type is the Arkansas River, whose headwaters are in 
the Sangre de Cristo, Culebra, and Sawatch mountains, in each of 
which there are summits exceeding 14,000 feet in altitude. The pre- 
cipitation along the crests of these high ranges is mainly in the form of 
snow and amounts to 20 or 30 inches of rain each year. From the 
foothills of the mountains to Arkansas City the rainfall ranges from 
12 to 35 inches; it is 25 to 35 inches in the last 100 miles below 
Hutchison. Natural storage in the Arkansas basin is limited to a few 
mountain lakes of glacial origin. The streams are subject to two 
floods per year — • the annual spring floods caused by the melting of the 
mountain snows, and the summer floods due to cloud-bursts in the foot- 
hills and plains regions.^ 

The Missouri River resembles the Arkansas in that its upper tribu- 
taries drain a forested region, while the main stream flows through a 
country almost wholly devoid of forests. The precipitation in the 
mountainous portion of the basin is mainly in the form of snow, but a 
great part of the area lies within the arid and the semi-arid regions, and 
it is probable that the mean annual precipitation throughout the entire 
basin is less than 20 inches. The river notably decreases in volume by 
evaporation in crossing the dry plains, though it never disappears, as 
is the case with many neighboring streams whose headwaters do not 
reach into the mountains.- 

In contrast to the Arkansas and the Missouri is the Red River, whose 
sources are on the plains of northern Texas. The flow of this river is 

1 Freeman, Lamb, and Bolster, Surface Water Supply of the United States, 1907-08, pt. 7, 
Lower Mississippi Basin, Water-Supply Paper U. S. Geol. Surv. No. 247, 1910, pp. 29-31. 

2 Follansbee and Stewart, Surface Water Supply of the United States, 1907-08, pt. 4, 
Missouri River Basin, Water-Supply Paper U. S. Geol. Surv. No. 246, 1910, p. 30. 



4IO FOREST PHYSIOGRAPHY 

very uncertain, the run-off consisting chiefly of flood water from heavy 
rains. The flow ceases entirely in the late summer and fall of ordinary 
dry years. The drainage area consists of semi-arid plains varied by 
small areas of sand hills. If the summer is dry, the flow of the river 
ceases altogether, although water sufi&cient for stock always remains 
standing in pools. During long-continued or unusually heavy rains, or 
directly after such rains, the river becomes wide and deep, its bottom 
lands are flooded, and considerable damage is often done to livestock, 
railroads, and plantations.^ 

Those streams that descend the eastern slopes of the uplands south of 
the Canadian River and near the New Mexico-Texas boundary line are 
of an extreme type and die out just eastward of the boundary line. 
Their waters are absorbed in the surface material or gathered in the 
form of temporary lakes. It is not until the central portion of the Pan- 
handle region of Texas is reached that the drainage is through-flowing 
and reaches the Gulf of Mexico by way of the Red River and other 
streams. 

Regional Illustrations 

northern great plains 

Many features of the northern part of the Great Plains in the United 
States owe their origin and character either to base-leveling or to glacial 
accumulation or both.- Westward from the valley of Red River of the 
North and the prairies of the Lake Winnipeg region is a plains country 
which rises gradually northwestward to the foot of the Rockies. The 
chief ascent of this plain west of the basin of Lakes Manitoba, Winnipeg, 
and Winnipegosis is over an abrupt escarpment developed upon Creta- 
ceous strata that form the eastern border of the continuation of the 
Great Plains in Canada. The escarpment is from 200 to 1000 feet high, 
and its sections are named in order from south to north, Coteau des 
Prairies, the Pembina, Riding and Duck mountains and the Pasquia 
Hills or Mountains. West of these hills and so-called mountains the 
broad expanse of plains is broken here and there by valleys and 
irregularly dissected tracts, but in general the surface appears to be 
very moderately rolling, rising 4 or 5 feet to the mile to a height of 
4000 feet at the foot of the Rocky Mountains in Montana and Alberta. 

At the beginning of Tertiary time this region became a land surface 

1 Follansbee and Stewart, Surface Water Supply of the United States, 1907-0S, pt. 4, 
Missouri River Basin, Water-Supply Paper U. S. Gaol. Surv. No. 246, 1910, p. 85. 

2 W. Upham, Tertiary and Early Quaternary Base-leveling in Minnesota, Manitoba, and 
Northwestward, (Abstract) Geol. Soc. Am., vol. 6, pp. 17-20. See also the American Geolo- 
gist, vol. 14, 1894, pp. 235-246. 



GREAT PLAINS 41I 

and has remained a land surface down to the present. During this long 
period (Tertiary) the great tract of country was base-leveled except for 
isolated residuals, here and there, consisting of remnants of horizontal 
Cretaceous strata elsewhere eroded. Turtle Mountain on the northern 
edge of North Dakota and the southern edge of Manitoba is an illus- 
tration of such a residual. It is about 40 miles long, about two-thirds 
as wide, and has an altitude of 200 to 800 feet above the surrounding 
country. It consists of nearly horizontally bedded shales and lignites 
capped by 50 to 75 feet of glacial drift. ^ West of Turtle Mountain the 
depth of the Tertiary base-leveling was greater and attained a tremen- 
dous value on the plains of Montana; in the Highwood and the Crazy 
Mountains districts the country was planed down 3000 to 5000 feet. 
These mountains owe their superior elevation to the great resistance of 
their rocks as compared with the strata wrapping about them ; they now 
stand as embossed forms rising conspicuously above the general expanse 
of the monotonous plains.- The greater denudation of the western por- 
tion of the Great Plains was due to greater initial uplift; it appears to 
have been raised 1000 to 5000 feet. 

The Tertiary topographic cycle of erosion was closed by a great 
uplift, after which vigorous stream erosion set in. In the eastern part 
of the Great Plains region erosion was carried to the point of partial 
base-leveling and the development of wide flat valleys. The Red River 
developed a broad plain more than 200 miles in extent from south to 
north and from 200 to 500 feet below the general level of the country. 
In Manitoba the Cretaceous beds were eroded down to the underlying 
Archaean and Paleozoic rocks over a large area and the eastern marginal 
escarpment formed. The depth of post-Tertiary erosion is indicated 
by the White Hills west of Lakes Winnipegosis and Manitoba, a long 
line of escarpments. During the period in which this escarpment was 
forming in Manitoba and in which its tributaries were deeply incised 
the plains of Montana were partly dissected by the deeply intrenched 
streams. 

These plains now present one of the best illustrations of an uplifted 
base-leveled surface to be found in the country. The surface bevels 
the strata of the region regardless of changing dip and hardness, con- 
sequently neither the structure of the rock nor alluviation can be 
appealed to in explanation of the general topographic uniformity. The 

1 W. Upham, Tertiary and Early Quaternary Base-leveling in Minnesota, Manitoba, and 
Northwestward, (Abstract) Geol. Soc. Am., vol. 6, pp. 17-20. See also the American Geolo- 
gist, vol. 14, 1S94, pp. 235-246. 

2 W. M. Davis, The United States in Mill's International Geography, 1900, p. 756. 



412 



FOREST PHYSIOGRAPHY 



interstream spaces are rather flat and give no indication of the marked 
depth and steep walls of the intrenched streams which are practically 
invisible until one is almost at the canyon brink. The narrow valley 
of the Missouri is from 300 to 600 feet below the general level of the 
plains, and that of the Yellowstone and many others have been cut to 
comparable levels. 



GLACIAL FEATURES 



The map, Fig. 148, shows how small a portion of the Great Plains has 
been glaciated. Besides glacial features similar to those of the northern 




Fig. 148. — Note the large proglacial lake west of the Highwood Mountains, caused by the glacial damming 
of the Missouri River. Its discharge across the northern border of the Highwood Mountains formed 
Shonkin Sag, a temporary outlet. (After Calhoun, U. S. Geol. Surv.) 

part of the Prairie Plains may be noted the two terminal moraines 
which cover the country north of the Little Rocky Mountains. The 
surface is a rolling plain with rounded flat-topped ridges and broad 
and low intervening hollows. The larger drift is chiefly Laurentian, 
but the bulk of the material is made up of quartzite drift from the 
Rocky Mountains, and consists of well-rounded pebbles and small 
quartzite bowlders of different colors.^ 

The Keewatin ice sheet extends southward into the northern Great 
Plains as far as the Highwood, Bear Paw, and Little Rocky Mountains. 
These elevations stopped its southward progress locally, while on the 

t Weed and Pirsson, Geology of the Little Rocky Mountains, Jour. Geol., voi. 4, i8g6, 
p. 402. 



GREAT PLAINS 413 

plains between it moved somewhat farther south in great lobes, Fig. 148. 
The Sweetgrass Hills, almost on the international boundary line (long. 
111° W.), were completely surrounded by the ice, above which they pro- 
jected 2000 feet as great nunataks. Terminal moraines therefore com- 
pletely encircle the hills, while the higher mountains farther south 
and east are but partly encircled by moraines. The position of these 
moraines along mountain slopes and on north-south lines makes it pos- 
sible to establish the fact that the slope of the ice surface was from 
30 to 50 feet per mile. A similar basis is afforded by the disposition of 
the moraines formed on the margins of lobes that extended up many 
of the valleys of the region, the divides between (150 feet high) remain- 
ing uncovered — with a similar result. 

Terminal moraines fringe the border of the drift-covered country 
in places only. Elsewhere there is no well-defined terminal ridge, only 
a broad low rise usually too slight to be noticeable. The terminal 
moraines are monotonously rough and their hollows contain large num- 
bers of smaller lakes and ponds. In places the moraines are bowldery 
ridges, in others they are broad belts of till of variable composition. 
Near the edge of the glaciated tract the drift is thin, though locally 
it is from 50 to 200 feet thick. 

The drainage of the glaciated northern portion of the Great Plains is 
toward the northeast and east, and ice invasion was therefore bound to 
block the streams either temporarily by the ice or more permanently 
by moraines or both. The lakes are of two classes. Those of the first 
class were in a few instances of great extent, and their floors are noted 
for the scattered bowlders rafted into position by detached ice blocks. 
The name Great Falls Lake has been given to one such temporary water 
body, formed by the ponding of the upper Missouri between the south- 
ward-facing ice sheet and the northward- facing slopes of the High wood 
Mountains. Its outlet along the northern mountain flanks at 3900 feet 
cut a broad channel nearly a mile wide and 500 feet deep, known as 
Shonkin Sag. It is one of the most striking topographic features in the 
region, since it is entirely independent of rock structure and crosses the 
present drainage lines at right angles. 

After the disappearance of the ice the terminal moraines continued 
for some time to act as barriers to the drainage, but outlets were soon 
cut down and the nearly bowlderless clays of the lake floors exposed. 
Most of the existing lakes of the region occur in the hollows of the 
morainic belts and are individually of small extent. 

Glacial features of considerable topographic prominence are also 
found upon the northwestern border of the Great Plains of the United 



414 FOREST PHYSIOGRAPHY 

States west of the limit of continental glaciation where valley glaciers 
from the front ranges of the Rockies deployed, building terminal and 
lateral moraines and supplying material for local alluviation (p. 312). 
The glaciers extended as individual tongues of ice down, the main 
valleys, but 14 of them united in groups along the base of the moun- 
tains to form piedmont glaciers of great size which extended out over 
the plains for from 30 to 35 miles. In other cases the ice extended only 
part way down the valleys, deposited valley moraines, and caused the 
formation of related features such as lakes, outwash plains, and valley 
trains. 

The piedmont glaciers and the continental ice sheet overrode com- 
mon ground in two localities — the headwaters of the Marias and 
St. Mary's rivers — though these ice bodies were not contemporane- 
ous. The valley glaciers had retreated before the continental ice sheet 
reached its greatest extension, since the deposits of the latter ice body 
overlie those of the former. The terminal moraines of the piedmont 
glaciers are of great size, some of them attaining heights of 200 feet 
and breadths of a mile or more.'- 

BADLANDS OF THE BLACK HILLS REGION 

Among the badland areas of the Great Plains the largest and most 
important is in South Dakota and Nebraska on the southern, south- 
western, and southeastern borders of the Black Hills. The portion of 
the badlands showing the greatest topographic complexity lies near the 
southeastern border of the Black Hills between the White and Cheyenne 
rivers and is known as the Big Badlands. It is continuous with a second 
badlands areas which extends eastward, southward, and westward along 
the upper White River forming the high Pine Ridge escarpment which 
extends through western Nebraska and into Wyoming. Outside the 
limits of the main badlands area are many remnants of the strata that 
formerly extended over the region. They now occur as mesas or tables 
which stand at various heights up to three hundred feet or more above 
the adjacent basin or valleys. Some of them are of large size and those 
east of the Cheyenne River have been given individual names by the 
settlers who occupy them, as Sheep Mountain Table, White River 
Table, Kuba Table, etc. The badlands were at first thought to be quite 
uninhabitable, the name itself being derived from the French name 
"Mauvaises Terres" applied by the early hunters and trappers. The 
phrase is meant to signify a country difficult to cross, chiefly because 

1 F. H. H. Calhoun, The Montana Lake of the Keewatin Ice Sheet, Prof. Paper U. S. Geol. 
Surv. No. 50, 1906. 



G-REAT PLAINS 



415 



of the rugged surface and the general lack of water. Later explora- 
tion and development have shown that much the greater portion of the 
area within the badlands is level and fertile and covered with abundant 
grass; and that water may be obtained, especially on the higher tables, 
by sinking shallow wells in the surface mantle of gravel. As a whole 
the region has considerable agricultural and grazing importance. 

The chief factors controlling the development of the badlands topog- 
raphy have been the great extent of slightly consolidated, fine-grained 
strata lying at a considerable altitude above the sea in a region of low 




Fig. 149. — Details of Badlands in Brule clay at foot of Scotts Bluff, Nebraska. (U. S. Geol. Surv.) 

rainfall and sparse vegetation. The scarcity of deep-rooted vegetation 
enables the soft material to be rather easily eroded. While short grasses 
are abundant over large areas they do not have deep root penetration 
and do not form a sufficiently continuous cover to prevent cutting. 
There is a small amount of vegetation of a higher order, but it is even 
less effective than the grass in preventing the formation of gullies. A 
few gnarled cedars occur on the highest points and bushes of various 
kinds occur in the valley floors in favorable places, but they offer little 
obstruction to the development of the gulches and canyons which diver- 
sify the scarped margins of the area. 



41 6 FOREST PHYSIOGRAPHY 

It is also noteworthy that the rainfall is more or less concentrated 
into heavy showers of short duration and these act most vigorously in 
denuding the surface, forming channels, and transporting accumulated 
rock waste. The clays which compose a large part of the. badlands 
expand greatly when wet and contract when dry (p. 415), so that their 
surfaces tend constantly to break up and form an easily eroded mass of 
material. Frost action tends toward the same effect, with the result 
that the clay is constantly being loosened in the dry as well as in the wet 
season, and is thus prepared for rapid erosion when rain falls. 

The topographic complexity of the badlands is explained chiefly by 
the unequal resistance to erosion on the part of, alternating beds. In- 
dividual layers vary horizontally as well, and the softer portions are 
worn back into the form of gulches and alcoves while the harder portions 
remain projecting as spurs or headlands. A hard layer tends to persist 
longer than a soft layer above or below it, thus forming typical scarp 
and terrace topography. In many cases the hard layer is undercut to 
such an extent as to develop a precipice. Joints are developed here and 
there in the clays and these tend to accelerate erosion along vertical 
planes with the result that cave-like excavations are formed at the 
heads of vertical walled gulches. Many beds contain large numbers of 
concretional masses whose resistance is greater than that of the surround- 
ing material, thus tending to the production of a surface whose irregu- 
larities reflect the irregularities of the concretions. 

Among the important topographic elements of the badlands are the 
alluvial fans which cling to the base of every pillar, mound, or table, 
and have a large total extent. Their surfaces have low gradients and 
they represent the lag of transportation behind disintegration. Most 
of the streams of the badlands area are intermittent. They have a 
continuous flow for a short time after the rainy season but their sources 
rapidly fail, and soon nothing is left in their channels but bars and banks 
of sand and silt, and a few trifling pools of water, either so strongly 
alkaline as to be of little value, or so turbid as to have the consistency 
of mud. Only two streams have a continuous flow, Cheyenne River and 
White River; but their flow varies greatly in volume, being high in the 
rainy season, when their tributaries are full, and very low in the dry 
season, when their tributaries fail. Many streams, especially the streams 
of medium size, flow in box-like trenches, the material of their banks 
standing up in bluff-like form as about the border of the area.^ 

1 For a summary description of the badlands of South Dakota, illustrated by well-selected 
photographs, see The Badland Formations of the Black Hills Region, C. C. O'Harra, Bull. 
S. D. School of Mines No. 9, 1910. 



GREAT PLAINS 



417 



HIGH PLAINS 

The map, Plate IV, indicates the extent of the High Plains, the most 
important subdivision of the Great Plains province. The interior topo- 
graphic and drainage features of the High Plains are typically represented 
in the Llano Estacado (Staked Plains) of Texas, the surface of which 
appears extremely flat to the eye, though it actually slopes eastward 
at the rate of 8 or 10 feet to the mile. Only gentle depressions occur 




Fig. 150. — Physiographic subdivisions of Te.xas and eastern New Mexico. (Hill, U. S. Geol. Surv.) 

here and there — the products of underground solution and of unequal 
wind erosion. Local storm floods tend to level these irregularities by 
filling the hollows and eroding the surrounding surface.^ 

The High Plains strata were laid down as a series of great compound 
alluvial fans or a piedmont alluvial plain at the eastern base of the 
Rocky Mountains. The eroded bedrock floor upon which the materials 
were deposited and the eroded condition of the materials themselves 

» R. T. Hill, Physical Geography of the Texas Region, Folio U. S. Geol. Surv. No. 3, igoo, 
p. 6, col. 3. 



4i8 



FOREST PHYSIOGRAPHY 



imply a succession of changes in the character of the stream action from 
degradation to aggradation and back again to degradation. These 
changes harmonize with the conception of climatic changes of known 




Fig. iji. — Ideal structure of the Tertiary deposits of the High Plains. The dark band indicates the 
position of a partly consolidated portion of the section known as a mortar bed. (Gould, U. S.-Geol. 
Surv.) 

occurrence, the dry Tertiary (aggradation) being succeeded by the wet 
Pleistocene (degradation), which was in turn succeeded by the dry 



Fig. 152. — Typical view of the High Plains of western Kansas. (Gilbert, U. S. Geol. Surv.) 



Present in which the streams are aggrading their valley floors.^ It is 
also conceivable that cutting power may have been gained or at least 
increased (i) by broad uplift on the west which would increase the 

1 D. W. Johnson, The High Plains, 20th and 21st Ann. Repts. U. S. Geol. Surv., 1898- 
1899, 1899-1900. 



GREAT PLAINS 419 

stream gradients and (2) by a cooling of the climate so as to reduce 
the evaporation. 

The greater part of the Tertiary deposits of the High Plains consists 
of clay, sandstone, and conglomerate, with clay largely predominating. 
The materials are usually arranged in a heterogeneous manner, as shown 
in Fig. 151, a characteristic dependent upon their origin as coarse 
channel or finer flood-plain deposits.^ A large part of the deposits is 
composed of smooth rounded white or yellow quartz grains locally 
cemented by lime into coarse rough sandstones, but more commonly 
unconsolidated and in places blown by the winds into dunes. In many 
instances the sand is mingled with small pebbles and clay cemented with 
lime, forming the so-called "mortar beds." The pebbles vary greatly 
in size, shape, and color, and generally occur in more or less lenticular 
cross-bedded layers, some of which are at least 50 feet thick. In many 
places they are mixed with fine sand and locally are scattered through 
the clay formations. 

The clays are generally white, but locally buff and pink in color. In places the lime cements 
the clay into irregular and grotesque forms, which, being harder than the surrounding forma- 
tions, are left standing in rehef by erosion and form picturesque elements in the local scenery .2 

The average thickness of the Tertiary deposits in eastern Colorado 
and western Kansas is 200 to 300 feet, but increases to nearly 1000 feet 
in portions of western Nebraska and southwestern Wyoming. Origi-, 
nally the entire region was probably covered with late Cretaceous 
deposits that extended far up the flanks of the Rocky Mountains, the 
Bighorn Mountains, and the Black Hills, a conclusion indicated by the 
occurrence of outliers of these deposits at high altitudes, the interven- 
ing portions having been extensively stripped off.^ 

PHYSICAL DEVELOPMENT 

After the great Rocky Mountain System on the west had been out- 
lined and during late Tertiary time there was a long period in which 
streams of moderate gradient drained across the central portion of 
the Great Plains. Locally, extensive lakes were formed, but the larger 
part of the deposits (Oligocene) of that time consists of coarse sand- 
stones, sands, etc., deposited on river flood plains and aggrading stream 
channels. Aggradation took place chiefly in Oligocene time, and the 
area of Oligocene deposits, Plate V, extends across the eastern part of 

1 C. N. Gould, Geology and Water Resources of the Panhandle, Texas, Water-Supply 
Paper U. S. Geol. Surv. No. igi, p. S3- 

2 Idem, p. 32. 

' N. H. Darton, Geology and Underground Water Resources of the Central Great Plains, 
Prof. Paper U. S. Geol. Surv. No. 32, 1905, pp. 169-170. 



420 FOREST PHYSIOGRAPHY 

Colorado and Wyoming, western Nebraska and South Dakota, and 
probably northward into Canada. The streams of this time shifted 
their courses from side to side and laid down a sheet of debris in the 
form of low-grade and confluent alluvial fans of vast extent and with a 
thickness in places of looo feet. The period of deposition ceased with 
the Miocene, and uplift and erosion followed which removed la.rge por- 
tions of the accumulated material. During this period of deposition 
(Oligocene) in the northern part of the High Plains the southern part 
was probably a region of erosion, but with the uplift and erosion of the 
northern High Plains (at the close of the Miocene) the southern por- 
tion became a region of deposition and the streams began depositing 
thin mantles of late Pliocene sands in southern Colorado, southern 
Nebraska, Kansas, and still more southerly localities.^ 

It is important to recognize that these changing conditions of late Tertiary deposition 
and erosion first in the north and then in the south were determined by diiierential uplift. 
The uplifted region suffered erosion, the depressed region suffered deposition. It is equally 
important to recognize the fact that these occurrences took place in the Tertiary under more 
or less stable climatic conditions and before the advent of the glacial ice. We have in these 
conditions clear evidence of broad differential uplifts and depressions which produce alter- 
nating conditions of aggradation and degradation over large areas during the Tertiary period, 
and which were, so far as we may judge, wholly unrelated to climatic influence except the 
general influence of aridity to leeward of the high Rocky Mountain Cordillera. The broad 
changes of later date are, however, undoubtedly to be associated with climatic change, though 
the exact locality in which erosion or deposition was strongest was probably determined by 
crustal movement. During the early Pleistocene uplift of the land there also occurred an 
increased precipitation which resulted in widespread degradation of the preceding deposits; 
the Tertiary deposits were entirely removed in the eastern portion of the area and widely and 
deeply trenched in the western pwrtion.^ There was deep erosion about the Black Hills dome, 
and the High Plains, whatever their extent in that direction, were largely removed and their 
northern edge left as at present in the great escarpment of Pine Ridge facing the Black Hills 
uplift. The streams of Pleistocene time also cut deeply and removed widely the high plains 
of Nebraska, Colorado, Kansas, and Texas, though wide areas of tabular surfaces are still 
exposed.' 

Descriptions of various portions of the High Plains vary greatly 
with reference to the present character of the stream work. It is fre- 
quently asserted that the High Plains are a region of denudation, 
although as frequently one finds the rivers described as building up the 
bottoms of their valleys. This contradiction is only apparent. The 
greater portion of the High Plains and many portions of the Great 
Plains are being denuded by the ramifying headwater streams, and the 

1 N. H. Darton, Geology and Underground Water Resources of the Central Great Plains, 
Prof. Paper U. S. Geol. Surv. No. 32, 1905, pp. 185-186. 

2 W. D. Johnson, The High Plains and their Utilization, 21st and 22nd Ann. Rept. U. S. 
Geol. Surv., pt. 4, 1899-1900, 1900-1901. 

3 N. H. Darton, Geology and Underground Water Resources of the Central Great Plains, 
Prof. Paper U. S. Geol. Surv. No. 32, 1905, pp. 186-188. 



GREAT PLAINS 42 1 

detritus is being carried down to the valley bottoms, where it accu- 
mulates in the form of broad valley flats or flood plains which to a large 
extent control the curves of the rivers, as along the valley of the Platte. 
Such aggradation is a normal result of the return to the drier conditions 
prevailing both now and in the Tertiary. The process will continue 
until a gradient is established which will allow the streams to carry 
all their waste to the sea. Dissection by the streams of Pleistocene 
time caused such a degree of valley cutting that the present aggrada- 
tion on the floors of the valleys is small compared with the degradation 
that preceded it. Consequently the tributaries of all the master streams 
of the High Plains region join valleys far below the general level. 
The tributary streams are therefore eroding the surface actively, and 
they drain by far the larger portion of the High Plains. Active erosion 
has stopped completely and active aggradation taken its place on almost 
all the larger valley floors. 

BORDER TOPOGRAPHY 

In some localities the erosion of the border of the High Plains has 
given rise to the formation of "holes" with local badland topography. 
A typical instance is Goshen Hole on the border of Wyoming and 
Nebraska. The formations which outcrop in this area consist largely 
of clays and sandstones. The clay (Brule) is easily eroded in such 
manner as to keep the sandstone (Arikaree) covering it in constant 
retreat as a nearly vertical wall about the edges of the Hole, a process 
greatly hastened by the issuance of ground water at the line of contact 
of the two formations. The escarpment separates the dissected low- 
land of the floor of the hole from the upland or general undissected 
surface of the High Plains. It is best defined upon the western side of 
Goshen Hole, owing to the absence of streams upon this portion, though 
the escarpment is here in constant retreat as the result of the sapping 
action of the ground water at the heads of the minor streams to which 
it gives rise. Upon the lowland constituting the floor of the hole are 
small mesas and tablelands, remnants of the upland that once occupied 
the region and that has since been worn away. Wherever the relations 
of drainage and geologic formations are such as not to bring the streams ■ 
below the soft strata or where the upper strata are soft and the lower 
strata hard, either a lowland has not been formed or, if formed, its bor- 
ders are not so well defined as in those cases where the softer members 
underHe the harder and the drainage has been developed distinctly 
below the level of the soft formations. 

The eastern border of the High Plains in Texas and Oklahoma is in 



422 



FOREST PHYSIOGRAPHY 



most places a distinct scarp 200 to 500 feet above the eroded plaiiis on 
the east, though ordinarily the descent is more gradual and takes place 
in a belt 5 or 6 miles wide — a belt with distinct topographic features 
in high contrast to the flatter plains to east and west."- This escarp- 







Fig. 153. — Jail Rock with the valley of North Platte in the distance, looking east. The capping stratum 
is sandstone (Gering) while the slopes are of clay (Brule). Typical border topography of a portion 
of the High Plains. (Darton, U. S. Geol. Surv.) 

ment is locally known as "The Breaks," Fig. 155. It occurs along the 
valley margins, passing in broad eastward-looping curves from one 
drainage system to another, and is characterized by badland erosion 




Fig. 154. — Eastern erosion escarpment of the High Plains of Texas, Oklahoma, and Kansas. The eroded 
bed-rock surface has been covered with Tertiary deposits and later ree.xposed in part. (Johnson, 
U. S. Geol. Surv.) 

forms, short ridges, steep talus slopes, isolated buttes and peaks, and 
an intricate system of narrow V-shaped valleys that sometimes develop 
into impassable canyons, Fig. 154. It is a region very difficult to trav- 

1 C. N. Gould, Geology and Water Resources of the Eastern Portion of the Panhandle of 
Texas, Water-Supply Paper U. S. Geol. Surv. No. 154, 1906, p. 9. 



GREAT PLAINS 



423 



erse, and can be crossed with a wagon only at infrequent intervals and 
by specially selected routes. The marginal escarpment is most typical 
along the Canadian River and in Palo Dura Canyon in i\rmstrong 
County, Texas. 




^i^ \ -^_ ^ \*l ^^ /< C\ 



w^-v 



!.^ 



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Fig. iSS- — Details of form, eastern border of the High Plains, Texas. The scarp is known as "The 
Breaks of the Plains." (Hill, U. S. Geol. Surv.) 

The eroded plains east of "The Breaks" have suffered such extensive 
dissection that the Tertiary and Pleistocene deposits have been en- 
tirely removed from their surface and the streams are actively dissect- 
ing the underlying Red Beds. The region is a rolling plain into which 
the streams are cutting rather deep steep-sided valleys, and outlining hills 
generally of conical shape but often elongated and attaining heights 
of 200 to 800 feet or more. These hills are capped by resistant ledges 
of sandstone, gypsum, or dolomite that have resisted the erosion which 
swept away the softer clays and shales above them.' 

SAND HILLS AND LAKES 

The sand hills of the Panhandle region of Texas range in size from 
small mounds to ridges 30 or 40 feet high. They are oval, crescentic, 
or elongated in shape and extend in various directions. They are inter- 
spersed with broad, shallow, basin-like depressions from i to 10 acres 
in extent, probably representing great ''blow-outs" or wind-eroded 
hollows. In a few localities there are migratory dunes, as on the west 

1 C. N. Gould, Geology and Water Resources of the Eastern Portion of the Panhandle of 
Texas, Water-Supply Paper U. S. Geol. Surv. No. 154, 1906, pp. 9-10. 



424 



FOREST PHYSIOGRAPHY 



side of the Canadian River in Roberts County. The dune sands are 
derived from sandstone ridges chiefly, but also in part from river sand. 
The rainfall on an important part of the southern High Plains is 
collected into shallow saucer-shaped depressions known as "lakes" or 
playa lakes, scattered irregularly about. The depressions vary in size 
from a diameter of a few feet and a depth of a foot or two to lakes 
several hundred rods in diameter and from 20 to 40 feet below the 
general level. Some of these depressions are more than a square mile 
in area. Many lakes in the depressions are perennial and afford an 



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Fig. 156. — Precipitation in the Texas Region. I, over 50 inches; II, over 45; III, over 40; IV, over 
3S; V, over 30; VI, over 25; VII, over 20; VIII, over 15; IX, over 10. (Hill, U. S. Geol. Surv.) 

abundant supply of water for stock. Others are ephemeral, that is, they 
are filled during a period of rain, but soon dry up; and still others con- 
tain water only at long intervals. Before wells were constructed and 
in the early settlement of the country the lakes were often in intimate 
relation to the location and welfare of settlers, for they constituted 
practically the only water supply. Wagon trains in crossing the Llano 
Estacado camped beside them, and they were centers to which cattle 
were driven until comparatively recent times. ^ 

1 C. N. Gould, Geology and Water Resources of the Panhandle, Texas, Water-Supply 
Paper U. S. Geol. Surv. No. 191, 1907. P. So. 



GREAT PLAINS 425 

The sand-hill country is not limited to the High Plains but is found 
(i) in many cases with limited development along the valley floors 
where sands deposited in the stream channels during high water become 
available to the winds during the low-water stages, as along the Arkansas, 
and (2) over the outcrop of unconsolidated material. The largest tract 
lies in Nebraska^ and was developed upon the outcrop of a sandy uncon- 
solidated formation which the present sand cover largely conceals. The 
thickness of the sand cover is rarely over 100 feet and generally much 
less. The total area of the tract is about 18,000 square miles. A 
peculiar feature of this great area is the relative absence of streams, 
except such as are supplied from outside sources. In spite of the small 
surface drainage there is considerable spring flow and seepage along the 
main river valleys. Most of the rainfall is absorbed by the loose dry 
sands and percolates downward, to be added to the ground water, which 
is surprisingly large in amount and is in general of good quality. The 
large amount of ground water is reflected in the numerous lakes scattered 
through the sand-hill country. Since the lake surfaces represent the 
surface of the ground water the lake levels rise and fall in response to 
the variable rainfall just as does the ground water. In times of light 
rainfall they are smaller and shallower; in times of heavy rainfall they 
are deeper and broader. Some of them disappear in extremely dry 
seasons; others are so permanent that their waters are stocked with fish. 
They are of great importance as a source of stock water, since the bunch- 
grass of the sand hills gives the area high value in respect of grazing, 
the chief industry of the region 

Vegetation 

Bunch-grass is the characteristic vegetal growth of the High Plains. 
Its growth is extended by roots and more rarely by seeds. The dryness 
and coarseness of the surface soil and its wind-swept condition render 
reproduction by seed very difiicult. The result is not a turf so dense 
that the ground is not visible but a series of tufts or bunches separated 
by large and small bare spaces.^ 

It is the general conclusion of students of the plains streams that 
floods are growing in volume and frequency, a state of things that is 
thought to be related largely to the breaking up of the protective grass 
cover by over-pasturage in the headwater regions. A grass cover has 
almost as great influence in checking run-off and favoring absorption 

> G. E. Condra, Geography of Nebraska, 1906, pp. 85-94. 

= Report upon Geographical and Geological Explorations and Surveys West of the looth 
Meridian (Wheeler Surveys), Geology, vol. 3, 1875, p. 606. 



426 



FOREST PHYSIOGRAPHY 



by the soil as a timber cover, and this relation is of such importance 
throughout the Great Plains region as to make it a point of great 
interest to the forester interested in general conservation, for the com- 
bination of grass-land and timber is thoroughly practical. 

In the middle courses of the Great Plains streams and on numerous 
tributaries in the mountains there is a protective timber covering. In 
a similar way a timber growth is found on the borders of the escarp- 
ments, and its maintenance is a matter of the liveliest concern to every 








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FiS- 157. — Vegetation of the Texas regions, i, Atlantic forest belt; 2, Rocky Mountain forest; 3, Chap- 
arral; 4, Black Prairie; 5, bolson desert flora; 6a, Grand Prairie; 6b. Great Plains; 7, transitional, 
with plains, prairie, and Atlantic flora; 8, coast prairies; XXX, yucca belts. (Hill, U. S. Geol. Surv.) 

one in any way related to the regime of the streams. The amount of 
washed soil running off in the floods that follow cloud-bursts in the 
Great Plains is enormous, especially where trees are absent and the 
grass covering thin; the maximum extent of grass and forest cover 
ought therefore to be maintained. This is seen especially in the lignitic 
belt of Texas, which is a rough broken country with sandy soils. But 
for the shortleaf and post-oak forests which cover them the soils would 
be washed in quantities from the steeper slopes. Annual plants with a 
superficial root system can not flourish in such soils without abundant 
rainfall. More than that, soils in these positions have little capacity 



GREAT PLAINS 427 

for retaining moisture, and forest growths are slow in beginning. The 
hills bordering the Edwards Plateau would become arid and worthless 
if they were stripped of their forest cover. The inch-deep soil debris 
would be rapidly washed away and the restoration of the forest become 
impossible. 

The Great Plains contain but little timber, though the supply is in 
many cases sufficient for local and limited use. In the Camp Clarke 
district of Nebraska the ridge extending west from Redington Gap 
bears scattered pine trees of moderate size, and there are also a few 
Rocky Mountain pines (Pinus ponderosa) on the slopes ascending to 
the high table at the southern margin of the district. The largest are 
from I to 2 feet in diameter. A moderate number of young pines 
begin growth in favorable situations on the ridges, though few of them 
attain maturity. The zone of cottonwoods is characteristic of most 
western streams, though it is absent along North Platte River, where 
only a few small trees and bushes are found. The principal deciduous 
growths are found in ravines; they include cottonwood, box elder, wild 
plum, and a few other varieties. '^ 

The Great Plains include much of the central treeless region of the 
United States where forest planting has been a part of the progress 
in agriculture, so that the areas of most extensive agricultural develop- 
ment are also those where greatest tree planting has taken place. Ap- 
proximately 840,000 acres have been planted in the central treeless 
region, but the best conditions can be obtained only by planting about 
14,000,000 acres in all. Although forest planting had been in a period 
of decline in this region, it has recently revived. It has been demon- 
strated that about 5% of the prairie region should be forest covered, 
and farther west, in the Great Plains proper, 3% could profitably be 
devoted to tree growing. South Dakota has planted about 122,000 
acres; Nebraska, about 192,000 acres; Kansas, 175,000 acres; Oklahoma, 
21,000 acres; Texas, 13,000 acres. The chief purpose of such tree 
planting has been for shelter, for post production, for protection from 
the hot winds of summer and the bhzzards of winter, and to a limited 
extent for fuel.^ 

A point of great interest in connection with the limited tree growth of 
the central plains is the possibility of an earlier and more extensive timber 
cover which may be restored by proper effort. If the rainfall was more 
abundant for a time during and after the retreat of the ice, it follows 
that timber may have grown upon areas now too dry to support it. The 

1 N. H. Darton, Camp Clarke Folio U. S. Geol. Surv. No. 87, 1903, p. i. 

2 Yearbook Dept. Agri., 1909, pp. 340-342. 



428 FOREST PHYSIOGRAPHY 

thought is the more plausible when we recognize the great length of time 
involved in the disappearance of the ice sheet, long enough, we may 
suppose, for considerable progress to have been made in natural 
reforestation. The conclusion appears to be supported by the finding 
of remnants of old pine forests in geologically recent deposits in the 
valley of the Niobrara, 50 miles southeast of existing forests of pine. 
It has been concluded that these forests formerly extended down near 
the mouth of the Niobrara.^ Likewise in the sand-hill country of 
Nebraska the stumps of cedars and pines — trees now confined almost 
wholly to the river bluffs — are found some distance away from the 
rivers, thus suggesting former more extensive tree growth.- 

The fundamental condition governing the treelessness of the Plains 
and the Prairies is the deficiency of rainfall in spite of the fact that 
the larger portion of the rainfall of the central plains region occurs in 
the summer or growing months, Fig. 22. Beyond the Mississippi the 
rainfall shades off rapidly; in sympathy with this increasing dryness is 
the gradual thinning out of the forest and its final disappearance. In 
the transition belt it is obvious that secondary forces will hold the balance 
of power. Among these undoubtedly the most important are the fine- 
ness of the soil, forest fires started by the Indians and by lightning, the 
prolonged droughts of exceptionally dry years, the high rate of evapo- 
ration of soil water, and the low humidity. 

The importance of the fineness of the soil has been strongly urged,^ 
since almost all forms of vegetation require an aerated soil, and this is 
true especially of all but a small number of forest trees. Prairie soils 
are notably fine and compact, especially in their natural state, and this 
tends to keep rainfall near the surface for a longer time than in the case 
of coarse soils, hence a larger part of the rainfall is reevaporated. The 
deeper-lying tree roots are thus deprived of a large part of the rainfall, 
besides being deprived by grass roots of such rainfall as is left available 
to plants. Prairie and forest fires are of frequent occurrence, and before 
the coming of the whites were often started by Indians either in sheer 
ignorance, carelessness, and wantonness, or for purposes of war and the 
chase. The number of thunderstorms that develop on the plains dur- 
ing the summer months is excessive. Lightning starts a fire in the dry 
half-withered grass and this spreads with great rapidity and is often not 
extinguished by the ensuing rain, which may be very light. Indeed 

1 S. Aughey, U. S. Geol. and Geog. Surv. of Col. and Adj. Terr. (Hayden Surveys), 1874, 
p. 266. 

- G. E. Condra, Geography of Nebraska, 1906, p. 93. 

3 J. D. Whitney, Plain, Prairie, and Forest, Am. Nat., vol. 10, 1876, pp. 577-588 and 656- 
667. 



GREAT PLAINS 429 

many summer thunderstorms are not accompanied by rain and fires 
burn unchecked. That this was formerly an important natural agent 
is shown by the extension of the natural forest upon prairie land in the 
Edwards Plateau of Texas.^ Settlement has stopped the periodic burn- 
ing of the grasses, which were harmed by fires much less than were the 
shrubs, the vanguard of the timber vegetation. The over-pasturing of 
the ranges of this region has prevented the grass from forming a con- 
tinuous sod, thus throwing further influence in the direction of the timber 
growth. In recent years the results have been marked. The shrubs 
have come in rapidly, trees have grown in their wake, and there is now 
in progress a gradual but extensive transition from grass to woody 
growth. 

The prolonged droughts of exceptionally dry years are effective in 
preventing the germination of the seeds of forest trees and in harming 
tender seedlings. At least three-fourths of the rain that sinks into the 
ground never gets beyond the surface layer of two feet,- while the increas- 
ing distance to the ground water with increasing aridity is well known. 
When these naturally hard conditions are enforced in exceptionally dry 
years the roots of seedlings and mature trees are confronted with grave 
difficulties in their search for a water supply. The water in the surface 
layer is soon evaporated in large part or left in the form of a film sur- 
rounding the soil grains where it ceases to be supplied by capillarity 
and gravitational flow to the root zone of forest trees. Evaporation is 
hastened by the high summer temperatures of the plains and the con- 
tinued sunshine and the rather steady and often high winds. 

It should not be forgotten in the analysis of the problem that the under- 
lying condition is regional dryness. Were the rainfall heavy, or even 
moderately heavy, a forest cover would undoubtedly exist in the plains 
country. Besides this factor the others appear secondary, yet the sum 
total of the secondary forces definitely restricts the forest, (i) There 
are far windier situations on forested mountain slopes that one may 
find on the plains, (2) forest fires do not eliminate trees from many 
relatively dry regions, (3) heavy clay lands bear luxuriant forests where 
rainfall and temperature conditions are normal. But when the condi- 
tions of rainfall are critical the balance of power is held by otherwise 
feeble influences. 

That the cause is not wholly climatic is reasonably inferred from the 
success with which tree planting has been conducted in the treeless 

" W. L. Bray, The Timber of the Edwards Plateau of Texas, Bull. Bur. For. No. 4g, 1904, 
pp. 14-15. 

2 F. H. King, Productivity of Soils, Science, n. s., vol. S3> iQn, p. 616. 



43° FOREST PHYSIOGRAPHY 

settled portions of the western country where windbreaks, snowbreaks, 
thrifty groves in city parks, etc., testify to the possibilities of at least 
a restricted reforestation. Even the sand dunes of Nebraska appear 
to be reclaimable, as shown by the at least temporary success that has 
attended the reforestation efforts of the government. The whole plains 
country can not be reforested since the greater part of it is too dry, but 
a large part will support a limited forest cover and the Prairie Plains 
can be made to grow trees almost everywhere, where now the growth is 
limited, at least toward the western border, to the valley floors and 
borders, and to tracts of porous soil with a good water supply. 



CHAPTER XXIII 

MINOR PLATEAUS, MOUNTAIN GROUPS, AND RANGES OF 
THE PLAINS COUNTRY 



Edwards Plateau 

The combined Edwards Plateau and Llano Estacado (the portion of 
the High Plains that lies in western Texas) is the most extensive relief 
feature of the non-mountainous part of Texas, with an area of about 










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Fig. 158. — Llano Estacado, Edwards Plateau, and adjacent territory. The central denuded rcgiuu was 
once covered with the Edwards limestone now exposed about the border as a frayed escarpment of 
erosion. (Hill, U. S. Geol. Surv.) 

431 



432 



FOREST PHYSIOGRAPHY 



60,000 square miles. The two merge into each other and no sharp line 
can be drawn between them. They are surrounded on all sides by 
pronounced escarpments. The eastern margin is an escarpment of 
headwater erosion, the southern margin is the dissected Balcones fault 
scarp, and the western and northern margins descend steeply to the 
drainage grooves of the Pecos and the Canadian respectively. 

While the Edwards Plateau continues the High Plains of western 
Texas or the Llano Estacado southward, it presents structural conditions 
wholly different from those found in the High Plains and, except for the 
general plain-like character of much of the surface, is quite different in 
its topographic character. It should be regarded as a subdivision of the 




X^ ^-^c:^ 



Fig. 159. — -Summits of the Lampasas Plain, Texas. (Hill, U. S. Geol. Surv.) 

Great Plains province and not as a portion of the High Plains. The 
surface of the Edwards Plateau is capped by the Edwards limestone, 
the most conspicuous and extensive sedimentary formation in Texas (and 
a large part of Mexico) inland from the coastal plain. The Edwards 
limestone is also important topographically, for its harder strata resist 
erosion to a greater degree than associated formations, and it is on this 
account the chief structural factor in the formation of the scarps, mesas, 
and buttes of the Grand Prairie, Edwards Plateau, and large portions of 
the limestone mountains of Mexico.^ 

The wide, flat, upper surface of the Edwards Plateau is terminated on 
the borders of the province by a pronounced descent, a ragged scarp 
due to the dissection of the draining streams whose irregular interlock- 
ing headwaters have cut up the border into innumerable circular mesas 

1 Hill and Vaushan, Nueces Folio U. S. Geol. Surv. No. 424, i8g8, p. ,^. 



PLATEAUS AND RANGES OF THE PLAINS COUNTRY 433 

and buttes. The descent from the level plateau to the canyons is over 
a cornice layer of hard rock that weathers into a nearly horizontal ver- 
tical bluff. At intermediate levels on the walls of canyons and valleys 
cliff makers occur; the intervening spaces between cliff makers consist 
of more easily weathered beds that yield a sloping talus. Fig. 155 
represents typical features in the eastern border of the plateau. 

The drainage of the plateau summit except in the case of the largest 
streams is of the intermittent variety, and in places even some of the 
larger streams disappear for a short distance. This is due partly to 




Fig. 160. ■ 



Summits of the Callahan Divide on the Great Plains of Texas (Central Province of Fig. ij 
(U. S. Geol. Surv.) 



evaporation, which is especially strong under the cloudless skies of 
western Texas, but in larger degree to absorption in the waste-filled 
valley floors or in the fissured limestone. The smaller streams have 
been called streams of gravel rather than streams of water, so clogged 
do their valley floors appear. The streams draining the border of the 
plateau have a very much more regular flow than might be expected 
because of the large number of springs which are fed by fissures and 
underground channels into which the absorbed water is directed. 

A subdivision of the Edwards Plateau is the Stockton Plateau west 
of the Pecos and east of the front ranges of the Trans-Pecos region. 
The southern border of the Stockton Plateau is tilted and faulted into 
low monocHnal blocks, while the scarps of the northern border overlook 
the Toy ah basin. 

Formerly the Edwards Plateau extended farther eastward, a condition 



434 FOREST PHYSIOGRAPHY 

shown by the erosion remnants now occurring as outliers beyond the 
eastern border of the plateau. These remnants consist of circular flat- 
topped hills and groups of hills on the interfluves. The summits of the 
outUers are all of the same geologic formation as the adjacent plateau 
and are in vertical alignment with the normal coastward slope."^ The 
altitude of these outlying mesas is about 500 feet above the principal 
stream courses and about 250 feet above the surrounding plains. They 
form less than 10% of the total area, although they are widely dis- 
tributed. The principal group occurs on the 31st parallel on the divide 
between the Brazos and the Colorado and is known under the collective 
name of the Callahan Divide. As a group these remnants represent a 
former broad topographic level that once extended from the mountains 
of the west to the eastern border of the Grand Prairie of Texas, p. 493. 
During and since the Tertiary this old level was largely destroyed in the 
central region of Texas and two opposing escarpments formed — the 
eastern border of the Edwards Plateau and the western border of 
the Grand Prairie — which are retreating from each other at the present 
time. Although the Balcones escarpment is commonly referred to as a 
fault scarp it should be noted that a portion of the descent is to be 
attributed to the increased steepness of dip along the front of a mono- 
clinal fold which has been still further accentuated by erosion, Fig. 162. 
The northeastern extension of the Edwards Plateau forms a third sub- 
division of the province. Its surface is structural in origin, as indicated 
by the large number of flat-topped remnantal summits which dominate 
the tract. They are developed most extensively on the divides between 
the drainage lines and in places have sufficient height to be called 
mountains. In general the plateau remnants are bordered by bare 
white limestone cliffs above and by gentler waste slopes below. The 
flat summits consist of weathered limestone in places without soil, in 
other places bearing a thin but rich soil cover. The largest continuous 
area of these remnants is called the Lampasas Plain which extends for 
115 miles from the Colorado in Travis County to the northeast corner of 
Comanche County, Fig. 160. As shown in Fig. 159, there is an intimate 
relation between the topography and the geology on the one hand and 
the vegetation on the other. From the scrub oak and post oak growths 
of the summit with its thin soils one passes in downward succession over 
the nearly soilless clift"s with a growth of shin oak to the deeper soils of the 
sandy formations with their good forests of black jack and post oak.'^ 

1 R. T. Hill, The Physical Geography of the Texas Region, Folio U. S. Geol. Surv. No. 3, 
1900, p. 6, col. 4. 

2 R. T. Hill, Geography and Geology of the Black and Grand Prairies, Texas, 21st Ann. 
Rept. U. S. Geol. Surv., p. 7, 1899-1900, p. 77 at seq. 



PLATEAUS AND RANGES OF THE PLAINS COUNTRY 435 



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436 FOREST PHYSIOGRAPHY 

PHYSIOGRAPHIC DEVELOPMENT 

The main mass of the Edwards Plateau was elevated into permanent 
dry land at the close of the Cretaceous period. During the Eocene 
period there was extensive erosion and the upper Cretaceous forma- 
tions (3000 feet) were swept away. Near the close of the Eocene, fold- 
ing and faulting took place and the Balcones fault scarp that limits the 
plateau on the south was outlined. During the Miocene the plateau 
was still further stripped and the Edwards limestone that now forms the 
surface of the plateau was exposed. Active erosion has continued from 
the early Pleistocene down to the present day. At the time of its ap- 
pearance above sea level at the close of the Cretaceous the Edwards 
Plateau region probably had topographic features similar to those ex- 
hibited to-day. The strong differences between the alternating strata 
resulted in wide stripping wherever the upper surface of a harder 
stratum of wide extent was exposed. 

SOIL COVER 

The soils of the Edwards Plateau are residual and consist in large 
part of chert nodules that have resisted solution and ordinary wear 
much better than the soluble limestone. With these are found impuri- 
ties common to limestone everywhere and even a certain proportion of 
the calcareous element. Upon the higher levels where flattish summits 
prevail the soils are good, but along the stream courses they are usually 
rough and stony. 

VEGETATION 

The most important topographic elements of the Edwards Plateau 
from the standpoint of vegetation are (i) the flat- topped summits of 
the plateau on the divides, (2) the "breaks" or scarps and related slopes 
of its ragged canyoned border, known locally as "the mountains," and 
(3) the streamways and their tributaries. The ragged escarpment which 
borders the plateau rises from 400 to 1000 feet above the coastal plain, 
and it is chiefly on this border that rainfall occurs.^ 

The Edwards limestone has a high absorptive capacity because of its 
low dip and the extensive system of fissures and caverns developed in 
it. These structures operate also to convey a large part of the water to 
the deeper strata, from which it discharges as spring water on the valley 

I W. L. Bray, The Timber of the Edwards Plateau of Texas: its Relation to Climate, Water 
Supply, and Soil, Bull. U. S. Bur. For. No. 49, 1904, p. 9. 



PLATEAUS AND RANGES OF THE PLAINS COUNTRY 437 

margins. The border region of the plateau is so deeply dissected that 
were the water not detained by a vegetal covering it would flow off 
after a heavy rainfall before it had time to enter the limestone, and 
the streams would have such volume and velocity as to cause swift and 
destructive floods. 

The Edwards Plateau is not covered with continuous forests even in 
the most favorable situations. The timber is much interrupted by open 




E^ 



Fig. 163. 



Escarpment timber of the Edwards Plateau. 
(U. S. Bur. of For.) 



Cooral River near its source. 



grassy uplands. Tongues of luxuriant forest follow the stream-ways 
into the center of the limestone region and in the deeper, well-watered, 
sheltered canyons the trees attain large dimensions. The forest is in 
the form of a thick-canopied, shady cover protecting many shade-loving 
shrubs. This floral community is altogether unlike that found in the ad- 
jacent country. It is distinctly like the Atlantic type, from which it is 
separated by miles of treeless country. The chief representatives are the 
American elm, sycamore, pecan, cottonwood, walnut, black cherry, etc., 
and in some places cypress with a diameter of 5 feet or more and a corre- 



438 FOREST PHYSIOGRAPHY 

spending height. The timbered belt is confined rather strictly to the 
deeply eroded portions of the plateau, gradually giving way to prairie 
on the level uplands toward the west and to grassy plains toward the 
east. There is a gradual dwarfing and thinning out of the heavy 
timber as one passes from the generally heavy growth of the watered 
canyons to the stunted forests of the hills and bluffs and the still scan- 
tier tree growth of the loose stony slopes. Finally there remain only 
scattered chaparral and the vegetation of the low Sotol Country, 
Fig. 157, whose principal representatives are sotol, cactus, yucca, and 
agave. 

The hill and bluff forest occurs on the " breaks "of the Colorado along 
the escarpment front from Austin westward and on the Guadalupe, 
the Pedronalles, and the Freio. It also extends northward upon the 
breaks of the Grand Prairie and the jagged hills of the granite country. 
The timber of this type varies in density with local conditions. On 
lower flats where deep black soil occurs there is a heavy mixed growth 
of cedar, live oak, elm, hackberry, mountain oak, shin oak, etc., and the 
type is extended to the side gorges and draws leading from the main 
stream-ways. Ten miles northwest of Austin on the Colorado are some 
timber-capped buttes, and similar occurrences are found in a few other 
localities. On the unstable talus slopes, where the natural shortage of 
water is emphasized by the excessive porosity of the loose debris, no 
timber covering is found except a scattered growth of mountain cedar.^ 
Juniper and laurel occur along the vertical slopes of the scarps and 
sometimes encircle the hills with bands of evergreen. On the floors of 
the drier valleys are tongue-like extensions of the chaparral flora of the 
Rio Grande Valley. They are characterized by thorny deciduous trees, 
mostly acacias, with an undergrowth of Mexican nopal. Thick-skinned 
yucca, ixtle, and cacti are also found as true desert flora on the bare 
limestone of the numerous buttes about the borders of the plateau. 

On the broken limestone areas are the "oak shinneries, " marked by 
a predominating growth of oak or dwarf shin oak. These are simply 
dense thickets, scarcely more than tall shrubbery, as on the divides be- 
tween the Colorado and the San Gabriel drainage country in Burnett 
County, where much of the growth is so dense as to make it impossible 
to ride through on horseback. Though it has no value as timber it is a 
soil retainer of great value. Mixed with this growth is a certain amount of 
live oak, mountain oak, plum, sumach, holly, and a number of climbers.^ 

1 W. L. Bray, The Timber of the Edwards Plateau of Texas: its Relation to Climate, Water 
Supply, and Soil, Bull. U. S. Bur. For. No. 49, 1904, pp. 15-17. 

2 Idem, pp. 17, 18. 



PLATEAUS AND RANGES OF THE PLAINS COUNTRY 439 

Among the most valuable assets of the Edwards Plateau region are the 
cedar brakes conspicuous on the white arid hills of crumbly limestone 
where the cedar is the dominant and practically the only species. It also 
grows in mixture with other species, attaining its largest growth in the 
mixed forests of the lower uplands, where the water supply and soil con- 
ditions are better. The most extensive bodies of cedar are those of the 
Colorado River brakes from Austin to the San Saba country.^ The cedar 
brakes are dry and as likely to burn as a prairie of tall grass. Evidences 
of ancient or recent fires are found almost everywhere. 

Many of the trees of the Edwards Plateau region are peculiar prod- 
ucts of their environment. 

"The eastern red cedar here becomes the mountain cedar; black walnut is represented by 
the Mexican walnut, whose nuts are tiny balls scarcely half an inch in diameter. Texas oak 
becomes mountain oak. The common live oak becomes a new form in its mountain habitat. 
The common persimmon is represented by the Mexican persimmon, whose fruit is a dark 
blue-black; Canadian redbud is here also a characteristic 'Judas-tree,' but of a dififerent 
species. The same is true in the case of the buckeye, mulberry, hackberry, and still others." 2 

The type of vegetation in the Edwards Plateau is undergoing a 
transition from grass to woody growth. The mesquite is capturing 
the open pastures, and the scrub oak occupying uplands that were for- 
merly open prairies. The transition is due to a number of causes. 
The ridges have been over-pastured and the balance of power thus 
thrown to the shrubs which are the vanguard of a timber covering. 
Twenty-five years ago the prairie held sway over large areas where 
now one finds scrub oak on every side. A great deal of the "shin- 
nery country" undoubtedl}^ represents a recent gain in timber on the 
prairie divides; from the edge of the brush each year new sprouts or 
seedlings are pushed out a few feet farther, and the new growths soon 
offer shelter for others. These scattered vanguards were formerly killed 
by the prairie fires and the timber growth held in check; but with the 
spread of settlements prairie fires have been reduced and a means of 
holding its position withdrawn from the grass covering. 

One of the most striking aspects of this encroachment of the timber 
upon the prairie land has been the spread of mesquite over the cattle 
country. Pastures have often been covered with a thicket as close as 
that of scrub oak, in which, however, the mesquite forms an open 
orchard-like growth with which are finally associated various species of 
chaparral and very commonly the prickly pear and the Opuntia. The 
final result of the spreading of mesquite is a heavy covering of vege- 

1 W. L. Bray, The Timber of the Edwards Plateau of Texas: its Relation to Climate, Water 
Supply, and Soil, Bull. U. S. Bur. For. No. 49, 1904, p. 19. 

2 Idem, p. 15. 



440 FOREST PHYSIOGRAPHY 

tation which serves as a protector of water supply and soil, although the 
original grassy growth would be of far greater value to man.^ 

Some of the interrelations of forests, water supply, temperature, and 
soils are peculiarly interesting. The forest covering furnishes shelter to 
the ground beneath from the sun's rays and prevents intense heating of 
the rocks and soils. A reduction of temperature is also afforded by the 
constant transpiration of water vapor from the leafage of the forest. A 
far more important effect, however, is the influence of the forest upon 
the soils. The foliage breaks the force of the rain and compels it to 
run harmlessly down the trunk or to drip slowly through the leaves. 
The direct impact of the falling raindrops upon the soil is thus pre- 
vented, erosion greatly diminished, and the absorption of the rain 
water promoted. Tending to the same result is the organic material 
of the forest floor, which holds back the fallen water until it has had 
time to soak into the soil. Thus gullying is prevented and frequent and 
destructive floods reduced in number and violence. These results are 
beneficial not only to the inhabitant of the region but also to those 
whose welfare is in any degree bound up with the regime of the streams. 
The rice planter on the coast is just as eager as the ranchman of the 
plains to have a constant and large flow of water, and the ranchman of 
the hills wishes his soils preserved and the soil moisture retained. For 
these purposes a forest cover, especially in a semi-arid region like the 
Edwards Plateau, is a vital necessity.^ 

Black Hills 

The Black Hills of southwestern South Dakota and adjacent por- 
tions of Nebraska and Wyoming rise several thousand feet above the 



Fig. 164. — Ideal east-west section across the Black Hills. Vertical scale six times the horizontal, i, 
slates and schists; 2, granite; 3, sandstone (Potsdam); 4, limestone (Carb.); 5, sandstone (Trias.); 
6, shales (Jura); 7, shales (Cret.); 8, shales (Tertiary). (After Newton.) 

surface of the surrounding plains. They have, by reason of their ele- 
vation, an abundant rainfall and as a result are well wooded, have 
many streams, and are in effect an oasis in a semi-arid region. They are 

> W. L. Bray, The Timber of the Edwards Plateau of Texas: its Relation to Climate, Water 
Supply, and Soil, Bull. U. S. Bur. For. No. 49, 1904, pp. 23, 24. 
2 Idem, pp. 26, 27, 29. 



PLATEAUS AND RANGES OF THE PLAINS COUNTRY 



441 



carved from a dome-shaped uplift of the earth's crust; the uphft has 
been sufficient to cause vigorous erosion, so that the upper layers 
once forming the top of the dome, and corresponding in age and charac- 
ter with the strata on the surface of the plains, have been removed by 
erosion, and the sedimentary rocks now exposed on some of the moun- 
tain summits of the Black Hills are older than those forming the surface 
of the Great Plains. The length of the Black Hills dome is about 100 
miles, the width 50 miles. The chief features are (i) a central area of 




Fig. 165. — Western slope of Black Hills southeast of Newcastle, Wyoming looking southeast. Steep- 
dipping beds are limestone, which spread out in a plateau at foot of slope. (Darton, U. S. Geol. Surv.) 



high ridges culminating in Harney Peak (7216 feet). This central area 
is composed of intrusive crystalline schists and granite of several varieties. 
(2) About the central crystalline area occur various concentric rings of 
sedimentary rock separated by well-developed valleys; the innermost 
mass of sedimentary rock occurs in the form of a limestone plateau with 
an infacing escarpment, Fig. 164. 

The limestone plateau slopes outward and extends around the Black 



442 FOREST PHYSIOGRAPHY 

Hills. Near its base there is a low ridge of limestone with a steep 
infacing escarpment from 40 to 50 feet high. The escarpments and 
slopes are sharply notched here and there by canyons which form char- 
acteristic "gates." Between this limestone plateau and the^ hogback 
ridge which constitutes the outer rim of the Hills is a depression, the 
Red Valley, which extends continuously about the uplift. The Red 
Valley is in many places two miles wide, though it is much narrower 
where the strata dip more steeply. It is one of the most conspicuous 
features of the region and is called the Red Valley on account of the 
red color of its soil. The outer hogback rim presents a steep face toward 
the Red Valley, above which it rises several hundred feet; on the outer 
side it slopes more or less steeply down to the plains that encircle the 
hills. It is crossed by numerous gaps and canyons which divide it into 
subordinate ridges of various lengths. 

The Black Hills dome was first developed either in early Tertiary or 
in late Cretaceous time, but the first uplift was to a moderate height. 
After this first uplift the larger topographic outlines of the region were 
established, the dome truncated, and its largest encircling valley ex- 
cavated in part to its present depth. Later deposits (Oligocene) were 
laid down by streams and in local lakes, and these deposits extend far 
up the flanks of the Black Hills, as at Lead and Bear Lodge moun- 
tains, respectively. After the deposition of these beds the Black Hills 
dome was raised several hundred feet higher and more extensively 
eroded, an erosion that has continued through Quaternary time and 
is in progress to-day.^ 

SOILS AND FORESTS 

The soils of the Black Hills region are closely related to the under- 
lying rocks and are of residual origin except on the valley floors and in 
a few cases where eolian action has taken place. On the limestone 
plateaus calcareous material forms the greater part of the rock. The 
soluble portions have been removed and the insoluble portions of 
clay and sand have collected as a soil mantle which varies in thickness 
with the character of the limestone, being thin where the limestone is 
pure, and thick where it contains many impurities. The amount of 
soil in a given region depends also on the rate of erosion. On many 
slopes erosion removes the soil as soon as it is formed, leaving bare rock 

1 Darton notes the occurrence of outliers of Tertiary (Oligocene and Miocene) deposits 
high up on the slopes of the Black Hills (N. H. Darton, Geology and Underground Water of 
South Dakota, Water-Supply Paper U. S. Geol. Surv. No. 227, 1909, pp. 26-27). 



PLATEAUS AND RANGES OF THE PLAINS COUNTRY 443 

surfaces; on others the surface is flat, erosion is not active, and the soil 
has accumulated to considerable depth. 

In the central core of crystalline schists and granites the rocks have 
been decomposed most by the dehydration of portions of their feldspar, 
with the result that the derived soil is usually a mixture of clay, quartz 
grains, mica, and other materials. The shales yield a sandy soil where 
they are sandy and a clayey soil where they themselves have been 
formed of relatively pure clay. In many cases the geologic forma- 
tions alternate in short distances; there are corresponding abrupt tran- 
sitions in the character of the soil in narrow parallel zones. Lack of 
sympathy between soils and underlying rock may be seen in the 
river bottoms, in sand dunes, in areas of high river gravels, and on 
slopes where soil derived by slope wash are mingled with or covered 
by soils derived in place. 

The Black Hills forest in general terminates abruptly at the broad 
valley known as the "Race Track," which lies between the main mass 
of the uplift and the lines of ridges which encircle the hills. The 
higher portions of the encircling ridges are also clothed with forest. 
Sometimes the growth in the latter case is good, sometimes it is in the 
form of a narrow summit fringe of trees. The main portion of the 
Black Hills forest includes about 2000 square miles of densely timbered 
territory. In many places the continuity of the forest is broken by parks 
and mountain prairies, and large tracts have been destroyed by forest 
fires which have swept the Black Hills periodically for years if not for 
centuries. 

The yellow pine is the only species of commercial importance; the 
others are either too small or have too specialized a use to have any 
great value. A few small bodies of spruce occur, and aspen has come in 
on some of the burned tracts. The best-quality pine is found in the 
side ravines and canyon bottoms, where soil and water supply are most 
favorable and where protection is afforded by the topography. On the 
steep slopes the soil is stony and thin, the drainage excessive, and the 
trees shorter and smaller. The forests on the north slopes are in gen- 
eral better than those on the south slopes because of (i) better pro- 
tection from fire and (2) greater water supply on account of lessened 
insolation.^ In general the limestone soils are more fertile than those 
derived from other kinds of rock and bear the most vigorous growths 
of trees. 

1 H. S. Graves, Black Hills Forest Reserve, 19th Ann. Rept. U. S. Geol. Surv., pt. 5, 1897-98, 
PP- 72-75- 



444 



FOREST PHYSIOGRAPHY 
Outlying Domes 



On the northern border of the Black Hills the Great Plains are diver- 
sified by a number of picturesque elevations that are unique topo- 
graphic features besides affording illustrations of a very peculiar type 




Fig. i66. ■ 



■ Devil's Tower from the north. The steep laccolithic mass is phonolite; the gentler slopes 
about it are developed on shales and sandstones. (Darton, U. S. Geol. Surv.) 



of structure. Each hill owes its existence to the injection from below 
of a column of molten rock into stratified beds. They are. not to be 
considered as volcanic necks, which they in some respects resemble, 
for the injected rock did not reach the surface so as to form either 
coulees or cinder cones. Named in general order from east to west 



PLATEAUS AND RANGES OF THE PLAINS COUNTRY 445 

the principal hills are Bear Butte, Custer Peak, Terry Peak, Black 
Butte, Crow Peak, in South Dakota, and the Inyan Kara, the Sun 
Dance Hills, Warren Peaks, Mato Tepee or the Devil's Tower, and the 
Little Missouri Buttes in Wyoming. 

As a group these hills display variety in the degree of erosion and 
hence in the degree of preservation of the original structures. In some 
cases the dome of stratified beds covering the injected rock is still un- 
broken and the plu tonic rock concealed; in others erosion has exposed the 
plutonic core, while in some erosion has progressed to the point where 
the central core stands forth as a tower of columnar rock (phonolite) 
several hundred feet in height. The first t3^e is illustrated by Little Sun 
Dance dome, which has very regular outlines, is about a mile in diameter, 
and deeply scored by erosion but not sufficiently eroded to expose the 
core of igneous rock that presumably lies underneath.^ 

The eroded type is illustrated by Mato Tepee, in which the arch of 
sedimentary rock has been entirely removed, exposing a column of 
injected rock. The tower stands on the west bank of the Belle Fourche 
River, quite by itself, and rises to a height of 626 feet above the plat- 
form on which it stands. The shaft of this magnificent natural column 
is composed of cluster prisms which extend from base to summit with- 
out cross divisions, each prism being a uniform unbroken column more 
than 500 feet high. Since the plateau on which Mato Tepee stands is 
itself about 500 feet above the river, it is clear that the minimum 
amount of erosion that must have taken place to expose the column 
is somewhat over 1000 feet. It was probably much over this amount, 
for none of the material of the Butte was extruded at the surface. There 
is good reason for believing that the amount of erosion in the region 
is but little under three-fourths of a mile, a conclusion which means that 
this great tower must have been buried under at least a half mile of 
sedimentary rock. 

Little Belt, Highwood, and Little Rocky Mountains 

In central Montana, just east of the front ranges of the Rocky Moun- 
tains, are a number of isolated mountain groups with structural and topo- 
graphic qualities totally different from those of the northern Rockies. 
On the east they break the continuity of the Great Plains of Montana 
and are prominent topographic features long before the traveler sights 
the Rocky Mountains. Lying east of or on the eastern border of the 
main Cordillera and in a region of deficient rainfall, their own sum- 

i I. C. Russell, Igneous Intrusions in the Neighborhood of the Black Hills of Dakota, 
Jour. Geol., vol. 4, 1896, pp. 23-43. 



446 FOREST PHYSIOGRAPHY 

mits rise to such heights, 5000 to 9000 feet, as to induce a greater rainfall 
than occurs on the surrounding plains, and they are therefore clothed 
with forests. Among these mountain groups are the Little Belt, High- 
wood, Little Rocky Mountains, and others. 

Little Belt Mountains 

The Little Belt Mountains are an elevated and eroded plateau, as 
shown on the accompanying topographic map. Fig 167. They are about 
60 miles wide from east to west and 40 miles from north to south on the 
west side, and taper to a sharp point at Judith Gap on the east, so that 
the group is roughly triangular in shape. Individual peaks along the 
northeastern border of the group rise above the general level and form 
an uneven crest line visible from the open plains. As compared with 
the well-defined ranges of the Rockies the Little Belt grOup is rela- 
tively low and wide and composed of many spurs radiating from a 
central point. ^ The border of the mountains on the west is defined by 
the deep canyon of Smith River, beyond which the country has gentler 
relief. 

On the summit of the Little Belt arch the rocks are gently inclined or 
horizontal, but on the flanks or shoulders of the arch the rock dips 
steeply away from the uplift. The intrusions which arched the beds 
are laccolithic in character. Since the development of its structural 
features the range has suffered extensive denudation. Erosion has 
laid bare the larger laccoliths and worn down the general level differ- 
entially; the harder igneous rocks have been left in relief to form 
the higher summits, while the softer sedimentary rocks have been 
eroded, although the members of each group have been eroded at 
very different rates owing to differences in degree of resistance. On 
account of' deficient height the Little Belt Mountains did not support 
local ice sheets during the glacial period, nor were they covered by 
the continental ice sheet during the time of its maximum southward 
extension.^ 

Throughout the greater part of the Little Belt region a plateau-like 
topography prevails; broad flat summits are characteristic. The aver- 
age elevation is 7600 feet, though the summit level from which the 
spurs radiate is 8000 feet high. The highest summit of the group is not 
at the center but along the northeastern border, where Big Baldy 
reaches an altitude of 9000 feet. The Little Belt Mountains are 

1 W. H. Weed, The Geology of the Little Belt Mountains, Mont., 20th Ann. Rept. U. S. 
Geol. Surv., pt. 3, 1898-1899, p. 273. 

2 Idem, p. 277. 



PLATEAUS AND RANGES OF THE PLAINS COUNTRY 447 







448 FOREST PHYSIOGRAPHY 

bounded by relatively soft rocks to whose deep erosion the prominence 
of the mountains is chiefly due. 

The relation of the detailed topographic features to the rock character 
is so intimate that it is impossible to distinguish the one feature without 
distinguishing the other. Summit plateaus are bordered by steep es- 
carpments with towering limestone cliffs along the stream gorges. 
Only the highest peaks along the northeastern border and the steep 
limestone gorges lend picturesqueness to the scenery. In the center 
of the mountain area where the beds are horizontal or only gently in- 
clined, secondary structural plateaus are commonly found. Upon some 
of these the rock is so resistant as to determine broad ridges which in 
some cases are emphasized by differences in soil and vegetation, as is 
the case in Belt Park and other timberless parks near Neihart, which 
have been developed on quartzite and which are in contrast with the 
wooded and soil-covered slopes above and below. There are no broad 
valleys within the mountains; for the most part the streams flow in 
deep trenches or narrow canyons in the harder limestone and in less 
narrow valleys in the shale belts. ^ 

CLIMATE, SOIL, AND VEGETATION 

Both rainfall and snowfall are relatively abundant in the Little Belt 
Mountains. Intermittent streams which flow only in wet weather or 
at times of melting snow are common. These are especially character- 
istic in limestone areas where the waters are absorbed by the porous 
and fissured rock and in those regions where the catchment areas are 
small. As a consequence of the greater precipitation due to the greater 
height of the Little Belt Mountains over the surrounding plains they 
are in general forest-clad, their dark slopes being in strong contrast to 
the arid treeless plains about them. Lodgepole pine is the prevailing 
species; in some places it forms forests with individual trees lo to 40 
inches in diameter, but usually it is much smaller. On the plateau 
summits the white pine is found, and spruce and fir grow along the 
wet stream bottoms and on moist and cold northern exposures. 

There is a very intimate relation between the character of the tree 
growth and the nature of the slope exposure. On southward-facing 
slopes, which are relatively dry because of the greater insolation, the 
growth is sparse and open, and interrupted by grassy parks; on north- 
ward-facing slopes thick and dark forests occur. The growth varies 
somewhat also with the character of the rock and the physical nature 

1 W. H. Weed, Geology of the Little Belt Mountains, Mont., 20th Ann. Kept. U. S. Geo!. 
Surv., pt. 3, 1898-99, p. 275. 



PLATEAUS AND RANGES OF THE PLAINS COUNTRY 449 

of the derived soil. The shales produce but little soil and support 
scanty vegetation; they usually underlie the park regions. The sand- 
stones and the igneous rocks are covered with land waste and are gen- 
erally densely wooded. 

HIGHWOOD MOUNTAINS 

The Highwood Mountains are a prominent member of the group of 
elevations that break the continuity of the northern Great Plains. They 
lie in the great bend of the Missouri in central Montana about 20 miles 
north of the Belt Mountains, and about 50 miles southwest of the Bear- 
paw Mountains, Fig. 148. About them stretch the smooth monotonous 
plains above which they rise about 4000 feet to summit elevations of 7600 
feet. The Highwoods are a group of old and now much eroded volcanoes 
which broke through the once fiat-lying Cretaceous strata of the plains. 
The mountains are composed chiefly of volcanic flows and breccias and 
a number of stocks or central cores, the remnants of former more lofty 
cones. The outer foothills are low and rounded; toward the center the 
country becomes more rugged. The descent to the plains is abrupt 
on the south; the chief feature of the northern slopes is an old glacial 
spillway known as Shonkin Sag whose origin is explained on p. 416. 
The drainage is in the main radial and consequent upon the original 
slopes of the volcanoes. The streams are rather constant in flow in the 
mountains but become sluggish and alkaline on the plains, some of them 
drying up in summer to such an extent that water remains only in pools 
in the deepest portions of the stream channels. The outer foothills 
and valley openings have been occupied by ranchmen who also utilize 
the water for limited irrigation. Extensive pastures are found on the 
higher slopes, though these give way to true forests of small pines on the 
northern exposures. In many places there are dense thickets of lodge- 
pole pine. The name ''Highwoods" undoubtedly had its origin in the 
forest growth of the northern si opes. ^ 

LITTLE ROCKY MOUNTAINS 

The Little Rocky Mountains lie about 200 miles east of the Rocky 
Mountain Cordillera and between the Missouri and the Milk about 60 
miles south of the 49th parallel. They rise from 2000 to 3000 feet 
above the treeless plains of central Montana, forming a conspicuous 
topographic feature in a plains region that is generally without 

1 L. V. Pirsson, Petrography and Geology of the Igneous Rocks of the Highwood Moun- 
tains, Montana, Bull. U. S. Geo!. Surv. No. 237, 1905, pp. 1-22. 



450 



FOREST PHYSIOGRAPHY 




PLATEAUS AND RANGES OF THE PLAINS COUNTRY 45 1 

prominent landmarks. Their topographic prominence led the Indians 
to call them "Eah hea Wwetan," or the "Island Mountains." 

The Little Rocky Mountains have an undulating crest without sharp 
peaks. The highest summit is more than 6500 feet above the sea, 
though only about half that height above the surrounding plains. The 
scenery is attractive but not grand, for the mountain summits are 
generally rounded, without that boldness that is the striking feature of 
most alpine scenery; and to this softness of outline is added the soften- 
ing effect of a thick growth of small pines, which covers almost all of the 
summits. Perhaps the most picturesque aspects of the mountains are 
developed about their borders, where heavily bedded limestones (Car- 
boniferous) are cut by deep narrow canyons variegated by a vegetation 
that stands in pleasing contrast to the dry plains. The limestones form 
a white wall encircling the mountains, and stream and cliff erosion has 
cut the thoroughly jointed beds into huge white scarps visible from 
points 50 miles away. Within the mountains the streams flow in deep 
V-shaped gorges. 

These mountains are formed upon a single dome-shaped uplift having 
a central core of crystalline schists overlain and marginally wrapped 
about by limestones (Paleozoic) and softer beds (Mesozoic).^ Hard 
and soft layers encircle and overlap the mountains and are crossed 
one after the other by streams consequent upon the original slopes of 
the uplift. Subsequent streams have developed along the strike of the 
softer beds and usually join the consequents where the valleys of the 
latter are broadest. The central core of crystalline schist is exposed 
in the headwater gorges of all the larger streams and in the deep-cut 
side slopes of the main crest. The gorges have heavily timbered slopes; 
the prevailing type of timber is the lodgepole pine, from 3 to 20 feet 
high. It is characteristic of the granite to have a covering of young 
pines; pines are found also upon the debris slopes, while the limestones 
and schist areas are covered by the big-leaf pine, which forms groves 
alternating with open parks. ^ 

Ozark Province 

The approximate limits of the Ozark region are the Missouri and 
Osage rivers on the north, the Arkansas on the south, the Neosho on 
the west, and the Black River on the east; the Shawnee Hills of southern 

1 Weed and Pirsson, Geology of the Little Rocky Mountains, Jour. Geol., vol. 4, 1896, 
pp. 399-428. 

2 Idem, p. 410. 



452 



FOREST PHYSIOGRAPHY 



Illinois, a continuation of the Ozark plateau, extend eastward to Shaw- 
neetown on the Ohio River. 

The Ozark region may be described as a broad, relatively flat-topped 
dome somewhat extensively dissected and consisting of three sub- 
divisions, the Salem Platform, the Springfield Structural Plain, and the 
Boston Mountains. The Springfield Plain inclines at a low angle 
toward the west in Missouri and toward the southwest in Arkansas, a 
slope which corresponds with the dip of the underlying formation. It 




Fig. 169. — Subdivisions of the Ozark region and relations to surrounding provinces. 
(Taff, U. S. Geol. Surv.) 



is deeply dissected by the large streams which flow through it in 
narrow valleys; the interfluves are large tracts of broad flat structural 
surfaces from which younger formations have been eroded. The 
Boston Mountains are capped by thin layers of sandstone and shale, 
the more resistant sandstone governing the physical features of the 
mountains. The rocks dip in the main to the south at an angle 
slightly greater than the general southward slope of the surface. From 
hilltops on the Springfield Plain the Boston Mountains appear as a 
bold, even escarpment with a level crest, but on closer examination the 
escarpment is seen to have many finger-Hke extensions to the north 



PLATEAUS AND RANGES OF THE PLAINS COUNTRY 453 

in the form of ridges and foothills. Toward the west the Boston 
Mountains decline in elevation and in ruggedness as the sandstone 
beds become thinner and more shaly in that direction. 

The Boston Mountains on the southern border of the Ozark province 
owe their dominating height in part to the excessive erosion of the region 
north of them and in part to differential uplift.^ The result of erosion 




Fig. 170. — • Topography of the Ozark region. (Purdue, U. S. Geol. Surv.) 



was to reduce a large part of the Ozark region in Missouri and Arkansas 
to a comparatively low altitude, leaving the Boston Mountains as re- 
siduals and their front as a rather bold escarpment. The former greater 
extent of the Boston Mountains is indicated by remnantal outliers 
standing several hundred feet above the general level of the area about 
them. In contrast to the northern part of the Ozark region, which is 
a low fiat dome with only local faulting and minor undulations, the 

> A. H. Purdue, Winslow Folio U. S. Geol. Surv. No. 154, p. 5, col. 4. 



454 FOREST PHYSIOGRAPHY 

Boston Mountains have a monoclinal structure and a correspondingly 
steeper border topography. 

The topographic forms of the Ozark region are those characteristic 
of early maturity in a region of nearly fiat-bedded rocks of varying 
hardness in which the dip of the rock and the slope of the surface are in 
many places coincident. The entire northern slope of the uplift is a 
succession of broad flat plateaus separated by more or less ragged es- 
carpments which mark the margins of the harder formations. For- 
ward from the escarpments there are scattered outliers, the fragments 
of more extensive layers separated from the escarpments by circum- 
erosion. The greatest dissection of the region is on the south and east, 
the least on the north. On the south and especially at the eastern end 
of the Boston Mountains the topography is rougher and the plateau 
character is all but lost. On the north the streams run commonly 
through broad and rather shallow valleys between which lie extensive 
areas of relatively undissected plateau. The drainage is in the main 
radial and consequent, the stream directions corresponding with the 



Fig. 171. — Topographic and structural section across the Ozark region along line A-A in Fig. 170. Shows 
the crystalline rocks of the St. Francis Mountains, the limestones of the Ozark Plateau, and "the shales, 
sandstones, and limestones of the Boston Mountains. 

restored slopes of the structural dome, but a certain amount of subse- 
quent stream development has also taken place where tributaries have 
excavated valleys along the outcrop of the softer formations. 

Seen from commanding points the surface of the Ozark region presents 
the appearance of an almost unbroken plateau due in part to the flat- 
ness of the structure but also and in larger part to peneplanation that 
once brought diverse structures to a common level which the vigorous 
erosion of the region since uplift has not yet wholly destroyed. 

The two main subdivisions of the Ozark Plateau, the Salem upland 
and the Springfield Plain, are separated by the Burlington escarpment, 
which runs in a general north-south direction.^ The escarpment is 
formed upon the border of a limestone layer (Mississippian) which con- 
stitutes the surface rock of the western part of the plateau. East of 
the escarpment, outliers of the limestone occur in the form of small 
residual areas between which are dissected plains bearing chert accu- 
mulations derived from the weathering and erosion of the limestone 

1 C. F. Marbut, Physical Features of Missouri, Missouri Geol. Surv., vol. 10, 1S96, pp. 11- 

IIO. 



PLATEAUS AND RANGES OF THE PLAINS COUNTRY 455 

that once extended over the entire region. The streams of the Salem 
upland flow in narrow valleys some of which are 250 feet or more deep. 
The degree of dissection is in some places so great that the former ex- 
tensive plain is not easily recognizable, though large interstream tracts 
still preserve their plain-like character. 

The Springfield upland on the other hand is largely a structural plain 
developed on the surface of the Mississippian limestone. Near the east- 
ern border of the upland the streams flow in shallow trough-like valleys 
which deepen westward as the streams cross low anticlines and domes. 
Those that drain the upland eastward have deep valleys where they 
cross the edge of the Mississippian limestone, which they have dissected 
to a ragged fringe. 

SOILS AND TREE GROWTH 

The soil of the Salem upland is cherty to a high degree, the chert 
having been derived from the overlying limestone. On weathering, the 
chert breaks into angular blocks and, because of its greater durability, 
forms a surface layer of debris. The finer soil particles produced by the 
weathering of the limestone are carried downward to the base of the 
weathered zone and are therefore at too great a depth to be accessible 
to agriculture, though they are of first importance to the forests, 
which seem to thrive in spite of the surface accumulations of loose 
stones. The most luxuriant forest is formed upon soils derived from 
the light-blue limestone and blue shales of the Morrow formation 
(Carboniferous). Walnut, locust, and other types found naturally only 
on fertile soils occur on this formation in spite of the fact that it out- 
crops usually on steep slopes. In general it may be said that in spite 
of the rather poor soils of the entire region, due to the cherty residual 
products resulting from the erosion of the limestone and also to the 
considerable dissection which the region is undergoing to-day, the sur- 
face is rather well occupied by forests, since it is too stony and steep to 
serve for other purposes and since the finer soil is washed down to too 
great a depth below the surface to be available for the ordinary plants 
of agriculture. 

Arkansas Valley 

South of the Boston Mountains is the Arkansas Valley district, which 
is structurally much more complex than the Ozark region, although 
standing at a lower elevation. The underlying strata have been thrown 
into overlapping folds which have been beveled off by erosion so com- 
pletely as to form a local peneplain approximately 800 feet above the 



45^ FOREST PHYSIOGRAPHY 

sea. It is surmounted, however, by residual peaks and ridges of small 
area and from 1700 to 2500 feet above sea level. Since the formation 
of the Arkansas Valley peneplain, uplift has occurred and the soft 
shaly beds have been worn away, leaving the inclined sandstones as 
low, narrow, and sharp-crested ridges whose summits are generally 
horizontal, a condition indicating the former elevation and topographic 
character of the area. 

Ouachita Mountains 

The Ouachita Mountains lie south of the Arkansas Valley and extend 
from Little Rock, Arkansas, westward into eastern Oklahom.a. The 
range is 200 miles long and nowhere rises more than a few thousand feet 
above the surrounding valleys and plains. The topographic forms of 
the range are developed upon an Appalachian type of structure, p. 585. 
Near the center of the range, long wide folds are developed upon 
massive sandstone; on the borders of the uplift are shorter and more 
complex folds developed upon shales and limestones as well as sand- 
stones.^ The regular development of hills or ridges and valleys is a 
striking feature of the group as contrasted with the irregularities of the 
igneous knobs and ridges of the Wichita Mountains of western Okla- 
homa. The regularity of the topographic details is absent in many 
places along the border, however, where faults with vertical displace- 
ments of several thousand feet have combined with the overturning of 
the folds to make the relief more irregular both in general plan and in 
detail. 

Arbuckle Mountains 

The Arbuckle Mountains form a triangular area approximately 30 
miles on each side with a westward extension. The western part of the 
Arbuckle Mountains has an elevation of about 1300 feet or 1400 feet 
above the plains on either side. The mountains were uplifted (late 
Carboniferous) and base-leveled in common with the great Appalachian 
province east of the Mississippi. Upon the base-leveled surface, then 
an almost flat plain, Cretaceous deposits were laid dowm. Later uplift 
caused the removal of the Cretaceous strata over large areas, but the 
superior hardness of the underlying rock has resulted in its preserva- 
tion in the form of a low plateau in the central part of the mountain 
group, while the bordering strata have been eroded to a lower level. 
The minor topographic details of the Arbuckle Mountains are due 
chiefly to the varying resistances of the rock formations. The lime- 

1 J. A. Taff, Structural Features of the Ouachita Mountain Range in Indian Territory, 
Science, n. s., vol. 11, 1900, pp. 187-188. 



PLATEAUS AND R.\NGES OF THE PLAINS COUNTRY 457 

stones in general are hard and form level-topped and narrow ridges with 
crests approximating the general plane of the regional uplift. Interven- 
ing soft cherts and shales are found in the wooded valleys that separate 
the ridges. In the more elevated part of the uplift erosion by swift 
s'*-.reams has etched the border of the plateau into a frill of deep gulches. 




Fig. 172. — Mixed hardwoods, etc., in typical relation to topography, Arbuckle Mountains, Oklahoma. 
On the dry limestone formations forests are absent, except along the lower and moister valley slopes 
and the valley floors. (Reeds, Oklahoma Geol. Surv.) 

A second and lower plain (probably Tertiary) occurs in the Wichita- 
Arbuckle region and descends approximately with the grade of the 
rivers. This plain merges into the Tertiary deposits of the coast on the 
one hand, and on the other hand stretches westward into Oklahoma and 
northward across Indian Territory. It is preserved through eastern 
and southeastern Oklahoma in innumerable ridges and hills, occurring 
at elevations approximating iSoo feet. A third erosion surface has 
been identified in the plains surrounding the Arbuckle Mountains; the 
larger streams have cut wide and flat valleys 200 feet below the gen- 
eral level of the Tertiary peneplain. This erosion surface is, however, 
much more fragmentary than either of the two surfaces just described. 
It is found bordering the Ouachita Mountains in the form of wide flat 
valleys developed upon the softer rocks. ^ 

Scrub Oak, Red Cedar, and Red Bud are the common trees on the 
mountain slopes, while red and white elm, Bois d'Arc or Osage orange, 

1 J. A. Taff, Preliminary Report on the Geology of the Arbuckle and Wichita Mountains 
in Indian Territory and Oklahoma, Prof. Paper U. S. Geol. Surv. No. 31, 1904, pp. 15-17. 



458 



FOREST PHYSIOGRAPHY 



hickory, pecan, hackberry, honey locust, river plum, papaw, mulberry, 
sycamore, willow, and cottonwood grow in the creek valleys and on the 
flood plains of the rivers like the Washita. There is also a striking 
increase in the timber growth (i) on the weaker formations (Sylvan 
and Simpson) which weather to lower levels, and (2) on those formations 
(Woodford and Reagan) which contain appreciable amounts of phos- 
phate and iron. The chert, shale, and sandstone strata, together with 
the granite and porphyry of the East and West Timbered Hills, are all 
covered with timber. In the narrow creek valleys and canyons, which 
have been developed on limestones (Arbuckle, Viola, and Hunton), trees 
appear on the alluvial deposits and near slopes, but rarely on the up- 
land surface. Fig. 172. The rainfall is notably heavier in the mountains 
than on the adjacent plains. Where the slopes are cleared for culti- 
vation the soil washes so badly that the clearings are soon abandoned. 
While the clearings are not abundant, yet in the aggregate they include 
an important and always a conspicuous part of the total area.^ 

Wichita Mountains 

The Wichita Mountains are the westernmost of the three mountain 
groups of the southern Great Plains. They are composed of igneous rock, 




Fig. 173- — Border topography, Wichita Mountains, Oklahoma. (Gould, Oklahoma Geol. Surv.) 

chiefly granite, and have been eroded into peaks varying in height 
from a few hundred feet to 1500 feet above the surrounding plains. 

1 The data for this paragraph have been supplied by Prof. C. A. Reed of Bryn Mawr 
College and Prof. C. A. Gould of the University of Oklahoma. 



PLATEAUS AND RANGES OF THE PLAINS COUNTRY 459 

The main range is about 30 miles long and 12 miles wide. West of it 
are a nmnber of scattered smaller ranges and peaks, such as Mount 
Tepee, Quartz Mountain, and Headwater Mountain. North and east is 
a 30-mile parallel range of hills composed chiefly of hard massive lime- 
stone, and the same limestone on the south and east occurs in the form 
of small rounded knobs. The limestone hills represent remnants of a 
series of rocks which once extended as a dome over the igneous rocks 
but which have since been deeply eroded. Between the granite and 
limestone ridges on the borders of the uplift are softer "Red Beds," 
shale and sandstone with local deposits of conglomerate, and these have 
been eroded to form valley lowlands whose extent corresponds to the 
outcrop of the less resistant strata.^ 

Mounts Scott and Baker are the highest mountains in the group and, 
like the numerous other peaks in the region, they have steep, rugged, 
bowlder-strewn slopes. Although the relative altitudes of peaks, ridges, 
and valleys are small, the mountains have a distinctly rugged appear- 
ance, with sharp outlines and narrow passes. There are more than 250 
detached areas of igneous rocks in the Wichita Mountains group, and 
these are expressed topographically in the form of a main mountain 
mass 150 square miles in extent and a large number of neighboring 
isolated sharp knobs which rise like islands above the smooth plains 
about them. The whole group forms an archipelago of granite moun- 
tains and peaks rising rather abruptly from the sea-like plains devel- 
oped upon softer rock.^ 

1 C. N. Gould, Geology and Water Resources of Oklahoma, Water-Supply Paper U. S. 
Geol. Surv. No. 148, 1905, p. 15; J. A. Taff, Prof. Paper U. S. Geol. Surv. No. 31, 1904. 

2 J. A. Taff, Preliminary Report on the Geology of the Arbuckle and Wichita Mountains 
in Indian Territory and Oklahoma, Prof. Paper U. S. Geol. Surv. No. 31, 1904, pp. 54, 77. 



CHAPTER XXIV 

PRAIRIE PLAINS 

Extent and Characteristics 

Between the great Laurentian area of Canada on the north and the 
Ozark-Appalachian provinces on the south and extending east and 
west from the Great Plains to the Appalachian Plateaus is a broad 
expanse of moderately rolling country known as the Prairies or Prairie 
Plains. The province includes the greater part of the Middle West, 
but it is not confined to that section of the country. It^ western por- 
tions are thinly timbered, the forest growth shading off to scattered 
groves of timber in lower and wetter localities or to the valley floors 
and the stream margins. Its eastern, better-watered portions are 
covered with a denser arboreal growth, though clearings are so exten- 
sive as to leave but insignificant patches of the primeval forest, and 
everywhere the timber is confined chiefly to w^ood-lots of limited and 
generally decreasing extent. The timber of the southern two-thirds of 
the Prairie Plains is prevailingly hardwood; on the north is a belt of 
coniferous forest which fills the gap between the northern edge of the 
hardwoods and the spruce forest belt of Canada. 

Although the Prairie Plains support a dense agricultural population 
and supply a disproportionately large part of the corn, wheat, oats, etc., 
of the country, they do not have an exceptionally favorable rainfall. 
It is certain that the agricultural products are far below the possibilities 
of the soil were a heavier and better distributed rainfall to occur. There 
is good reason for believing that were the surface less flat, the absorp- 
tion of rain water less pronounced, the original forest would have been 
much more restricted. 

The Prairie Plains belong to the vast central plains region between 
the Atlantic and the Pacific Cordillera and present from commanding 
points a number of characteristic views. In many places the province 
has the appearance of a limitless expanse of grove-dotted, gently undu- 
lating country, here and there trenched by rivers and surmounted by low 
hills ; or it stretches away as far as the eye can see without either of these 
relief features — a grass-covered, farm-dotted, smoothly contoured prairie. 
North of the Missouri and Ohio rivers it is glaciated. Morainic belts 
cross it in looped pattern, and between them are notably flat till plains. 

460 



PRAIRIE PLAINS 461 

In that portion covered by glacial ice in the last (Wisconsin) glacial in- 
vasion, lakes, ponds, and undrained hollows in great numbers are scattered 
freely about, stream courses are disorganized, falls and rapids abound 
and alternate with swampy depressions often of considerable extent. 
The southern portion of the glaciated tract and a part of the unglaciated 
area beyond are covered to a variable degree by loess deposits, — fine. 




Fig. 174. — Typical view of the Prairie Plains in the Great Lake region. Woodland tract in left 

foreground. 

light, wind- and stream-deposited detritus of great importance in relation 
to both run-off and soil fertility. East of the Mississippi the Prairie 
Plains grade southward into the Appalachian Plateaus; west of that 
river and south of the limit of glaciation they have a distinctive quality 
unlike any other portion of the province. In the Osage Prairie of eastern 
Kansas, and specifically about "Independence, they have the appearance 
of an ancient surface of erosion. Here broad valleys separated by low 
divides are characteristic features; none of the irregularities of glacial 
topography or drainage is found; in fact there is so little relief that water 
storage by dam construction is impracticable on account of the breadth 
of the valleys and their gentle gradients. 



462 FOREST PHYSIOGRAPHY 

THE PENEPLAIN OF THE PRAIRIES 

The most general topographic feature of the Prairie Plains is the 
Tertiary peneplain now standing at various elevations above its former 
level. It may be traced from central Texas northward through Okla- 
homa and Kansas into Wisconsin, Indiana, and southern Michigan. 
While it is now a dissected and therefore a discontinuous surface its for- 
mer character and wide extent may reasonably be inferred because large 
tracts are still in an excellent state of preservation. It is fair to assume 
that the Tertiary peneplain of the region was far more extensive than 
its visible remnants, now for the most part in process of dissection. The 
Tertiary peneplain appears to have been much more extensive in the 
upper Mississippi basin than was the corresponding plain in the Appa- 
lachian tract; the latter was limited largely to the belts of softer rock 
or to the larger streams. 

The uplifted peneplain was dissected to various stages of maturity 
before the Pleistocene period, so that by the beginning of that period 
pronounced valleys had been formed: in some places the valleys were 
narrow and the intervening divides wide, while in other places the val- 
leys were widely opened and the divides reduced to narrow ridges. The 
slopes of many valleys were steep and covered with a thin veneer of 
decayed rock, and almost the whole of the now glaciated country had a 
somewhat more rugged appearance than at present. 

The surface of the peneplain was not everywhere affected in the same 
way after its development. In some cases it was uplifted and broad 
valleys opened at lower levels, in other cases there appears to have 
been no uplift, in still others uplift appears to have been progressive 
and no opportunity given for the formation of a peneplain. Even with- 
out peneplanation the surface would nowhere have great relief, for this 
is distinctly a region of low-lying and nearly flat strata. The depth of 
erosion conditioned by the rainfall, the elevation, and the character of 
the rock would be a measure of the relief, unlike many mountain regions 
where the relief in the earliest stages of an erosion cycle is commxonly 
related directly to original structural irregularities. 

A description of a few typical occurrences will serve to show the 
general development of the peneplain of the prairies and its present 
condition. An ancient topographic level has been clearly determined in 
southwestern Wisconsin (Driftless Area). Fragments of the plain slope 
gently southward across the outcropping edges of shales, dolomites, and 
sandstones. In spite of the strong variations in resistance to erosion 
which these beveled strata display the plain truncates them with 



PRAIRIE PLAINS 463 

striking uniformity. It is therefore not a structural plain but a plain 
of erosion. It is typically developed about Lancaster, Wisconsin, where 
it stands about iioo feet above the sea. Since its formation it has 
been broadly uplifted and extensively dissected. The main valley bottoms 
lie several hundred feet below the general level of the uplifted peneplain 
and well-developed flood plains are common. Dissection has progressed 
to the point where the original plain surface now remains only along the 
stream divides, and the cubic contents of the valleys approximately equal 
the cubic contents of the ridges between the valleys.^ 

South of the Great Lake region the uplifted and dissected peneplain 
may be clearly identified. In eastern Missouri and in Illinois it has 
been described as a plain of wide extent now much dissected, its remnants 
being represented by the accordant hill and ridgetops. In a general 
view this regularity of level of the summit areas makes the sky line 
nearly flat, a dominating topographic feature. Such striking accordance 
of summit levels is the more significant when it is realized that the plane 
thus denoted truncates inclined strata offering very unequal resistances 
to erosion." 

In Indiana the surface appears to display two erosion levels forming 
an upper and a lower plain. The level summits of the higher hills and 
ridges mark the position of the now greatly dissected older topographic 
level about 600 feet above the sea. One hundred feet lower are rolling 
uplands which exhibit smooth, gently rounded hills and ridges or flat 
divides separated by broad and relatively shallow valleys.-^ 

In the prairie plains of eastern Kansas the uplift appears to have 
been insufficient to occasion dissection of the peneplain formed during 
the Tertiary. The beveling of the strata is here still in progress. The 
divides are smooth and broad, truncation is now in progress; if the land 
retains its present level there will be even more complete leveling of the 
surface, and the region will finally exhibit an ultimate base-leveled 
plain. All relation between structure and topography has, however, 
not yet vanished. In the Osage Prairie, for example, are broad structural 
terraces surmounted by a few outlying and isolated hills, though the 
relief is far less gentle and faint as compared with th ^ relief of the 
region during the earlier periods of the present erosion cycle. The 
terraces face eastward and have frontal scarps from 100 to 200 feet 

1 Grant and Burchard, Lancaster-Mineral Point Folio U. S. Gaol. Surv. No. 145, 1907, p. 2, 
cols. 1-2. 

2 N. M. Fenneman, Physiography of the St. Louis Area, Bull. 111. Geol. Surv. No. 12, 1909, 
pp. 17, 52. 

' Fuller and Clapp, Ditney Folio U. S. Geol. Surv. No. 84, 1902, p. i, col. 3. 



464 FOREST PHYSIOGRAPHY 

high. Each terrace has a long and relatively gentle westward slope 
whose total descent is less than the descent of the frontal scarp. Each 
terrace therefore stands above its neighbor on the east and below the 
next terrace on the west, so that the series rises in westward 'succession 
and the rate is about 10 feet per mile. The north-south drainage lines 
show a marked tendency to migrate down the dip of the indi\dduai 
terrace, i.e., westward; hence the eastern valley slopes are commonly 
gentle and low, the western, steep and high. Stream courses at right 
angles to the terrace fronts show alternations of broad open stretches 
on the terrace tops and narrow steep-sided stretches on the terrace 
fronts. 

Both the topographic and the drainage features are related to the 
structure in still other respects. The westward-dipping shales, sand- 










Fig. 175. — North-south section near Tishomingo, Oklahoma, showing the peneplaned surface of the 
Prairie Plains on the south. (Taff, U. S. Geol. Surv.) 

stones, and limestones are of variable thickness. Where the resist- 
ant sandstones are thick the topography is irregular and has marked 
relief; where the soft shales are thick and the resistant strata thin or 
absent the surface has very gentle gradients, broad valleys, and but 
little relief. The average elevation of the district is about 900 feet, and 
the difference in elevation between adjacent hills and valleys is from 
50 to 200 feet.^ 

Toward the south, as in Oklahoma and northern Texas, the Prairie 
Plains once more take on the character of an uplifted and dissected 
peneplain. Fig. 175. The uplift was not great, however, probably not 
more than 100 feet, and large remnants of the former featureless plain 
occur on the interfluves. The valley topography is a feature of the 
present cycle of erosion; the inter-valley topography exhibits many 
characters inherited from the preceding cycle of erosion in which a 
peneplain was formed.- 

1 F. C. Schrader, Independence Folio U. S. Geol. Surv. No. 159, 1908, pp. 1-5. 

2 J. A. Ta£E, Coalgate Folio U. S. Geol. Surv. No. 74, 1901. p. 4, col. 4., and C. N. Gould, 
Geology and Water Resources of Oklahoma, Water-Supply Paper U. S. Geol. Surv. No. 148, 
1905, p. 12. 



PRAIRIE PLAINS 



CENTERS OF GLACIATION ^ 



465 



The ice sheets which overrode the northern Prairie Plains originated 
in two centers of glaciation known as the Keewatin, west of Hudson 
Bay, and the Labrador, in the Labrador peninsula. A third, the 
Cordilleran center in northern British Columbia, is of little interest 
here, for it lay too remotely to the west to affect to an important degree 




Fig. 176. — The centers of ice accumulation, the position of the Driftless Area, and the southern limit of 
glaciation. (Alden, U. S. Geol. Surv.) 

the topography of the Plains, Fig. 176. The Keewatin glacier formed in 
a great gathering ground close to, the western coast of Hudson Bay, 
from which the ice radiated in all directions — eastward into Hudson 
Bay, northward to the Arctic Ocean, westward to the Mackenzie Val- 
ley, and southward toward Manitoba and the Great Plains. At or near 
the center of glaciation the striae are very indefinite and appear to 
have changed in direction as the center slightly shifted its position, but 
no evidence of more than one glaciation has been found, nor has it been 

1 J. B. Tyrrell, The Genesis of Lake Agassiz, Jour. Geol., vol. 4, 1896, pp. 811-815. 



466 FOREST PHYSIOGRAPHY 

determined that the ice left the country uncovered at any time during 
the glacial epoch. 

The Keewatin glacier advanced southward and southwestward until 
it came in contact with the high escarpment of Cretaceous -shales in 
eastern Manitoba, followed the course of Lake Winnipeg and Red 
River and in this direction advanced far into Minnesota, Dakota, and 
Iowa. The eastern margin of this lobe did not extend very far east of 
the present eastern shore of Lake Winnipeg, and it is probable that 
throughout its advance there was a free drainage eastward, probably 
into Hudson Bay. 

The evidences of the time of advance of the three continental ice caps 
which formed over northern North America go to show that these three 
seem to have reached their widest extent and to have retired in suc- 
cession from west to east, and -that a fourth ice cap, probably similar in 
character to those that have disappeared from the American continent, 
covers Greenland at the present time. 

Glacial and Interglacial Periods 

The different glacial and interglacial stages of the glacial period are 
numbered in the order of their occurrence below. ^ Their deposits are 
represented in part on the accompanying maps showing relations of 
the drift sheets in the Middle West. 

XIIL The Champlain substage (marine). 

XII. The glacio-lacustrine substage. 

XI. The Later Wisconsin, the sixth advance. 

X. The fifth interval of deglaciation, as yet unnamed. 

IX. The Earlier Wisconsin, the fifth invasion. 

VIII. The Peorian, the fourth interglacial interval. 

VII. The lowan, the fourth invasion. 

VI. The Sangamon, the third interglacial interval. 

V. The lUinoian, the third invasion. 

IV. The Yarmouth or Buchanan, the second interglacial interval. 

III. The Kansan, or second invasion now recognized. 

II. The Aftonian, the first known interglacial interval. 

I. The sub-Aftonian, Jerseyan, or Nebraskan, the earliest known 
invasion. 

I. The sub-Aftonian or Nebraskan ^ glacial stage is represented in Iowa 
as a very old drift sheet whose surface bears sand and gravel, peat, 

> Chamberlin and Salisbury, Geology, vol. 3, 1906, p. 382 Q. 
2 B. Shimek, Bull. Geol. Soc. Am., vol. 20, igog, p. 408. 



PRAIRIE PLAINS 467 

old soil, and other products of prolonged weathering. The Nebraskan 
drift consists largely of compact blue-black bowlder clay. In many places 
it is thickly set with woody material gathered from forests that were 
overwhelmed by the ice. The wood is largely spruce, cedar, or conifer- 
ous species that indicate a cool-temperature flora in advance of gla- 
ciation. The drift filled the deep preglacial valleys to depths of nearly 
350 feet, but it formed only a thin cover on the uplands, where it was 
nearly removed by erosion before the next glacial invasion.^ 

The interglacial stages are of little interest in the present connection. 
Rather typical conditions are represented by the first epoch in the 
series. 

II. The Aftonian interglacial stage is represented by sand and gravel deposits and by beds of 
peat and muck, with stumps and branches of trees, and shows prolonged erosion and weather- 
ing. Several bones of the camel have been found in the deposits of this epoch; also the antler 
and fragments of bones of a large stag, three species of elephant, the American mastodon, and a 
large variety of molluscan remains of both aquatic and terrestrial species. The fauna and flora 
indicate a climate not greatly different from the present, though the fossils merely represent 
the conditions at the time of their burial, and still leave largely to conjecture the full range of 
temperature of the period.' 

III. The Kansan glacial deposits, p. 473, occupy a large area in 
Kansas, Missouri, Iowa, and Nebraska and probably extend under the 
later glacial formations far to northward. The Kansan till is pro- 
nouncedly clayey and has very little water-laid material either within 
the body of the till or on its margin, where the usual fluvio-glacial 
deposits of sand and gravel are very meager. The surface of the Kansan 
till although originally quite flat has been considerably eroded and its 
topographic features notably altered from their original expression. 

It is estimated that the Kansan drift occupies only from 10% to 30% of the original plain. 
The streams flow in valleys with broad and low (3° to 5°) slopes and bottoms. The average drift 
removed by erosion in the exposed portion of the Kansas drift is estimated to be not less than 
50 feet. The material is deeply weathered and it has been deprived of its iiner and more readily 
dissolved calcareous material and even limestone pebbles down to 5 or 8 feet.^ 

V. The lUinoian till is chiefly clay and is similar to the Kansan till 
in showing a marked absence of assorted drift in most places. Drain- 
age modification brought about through the Illinoian glacial invasion in 
the Mississippi Valley is of uncommon interest. The western edge of 
the Illinoian ice lobe crossed the Mississippi Valley between Rock Island 
and Fort Madison, and pushed the Mississippi River out of its course a 
score of miles (p. 475). 

1 Frank Leverett, Comparison of North American and European Glacial Deposits, Zeitsch. 
f. Gletscherkunde, Berlin, vol. 4, 1910, p. 250. 

2 Idem, p. 253. 
s Idem, p. 258. 



468 FOREST PHYSIOGRAPHY 

The bowlder clay of the Illinoian drift appears originally to have been very calcareous but 
to have been leached since deposition to a depth of from 5 to 8 feet and nearly all the limestone 
pebbles completely removed. Much of the deposit has become partially cemented because 
of the large calcareous element in the drift. Where erosion has been most rapid it has destroyed 
scarcely more than half the original plain. ' 

VII. The lowan till is thin and is noteworthy for the exceptional 
number of large granitoid bowlders which lie chiefly on the surface. This 
drift was formed by a lobe of the Keewatin ice sheet. The moraines 
formed about the borders of the lobe were very feeble and the outwash 
scant. 

IX. The two Wisconsin ice sheets are the most important of all, not 
because of their greater original extent or their thicker drift deposits 
but because their drift deposits are the last of the series and have there- 
fore been more extensively preserved. The interval since the occurrence 
of these last glacial stages has been so brief, furthermore, that but 
little modification of topography, drainage, or soils, has been possible. 
The outermost limits of the Wisconsin ice sheets are marked in most 
places by pronounced terminal moraines, and in addition the surfaces of 
the till sheets are diversified by terminal moraines due to the periodic 
recession of the ice. Their surfaces are also diversified by various gla- 
cial and fluvio-glacial forms not developed, as a rule, on the deposits of the 
earlier glacial stages. The chief varieties of these deposits are the out- 
wash plains formed by streams discharging from the ice front, also 
kames, eskers, and drumlins. In a number of noteworthy cases these 
forms have a marked tendency toward aggregation. The Sun Prairie 
topographic sheet of Wisconsin represents the remarkable drumlin 
accumulations of that and adjacent portions of the state; and a similar 
swarm of drumlins may be seen in central New York between the Finger 
Lake district and Lake Ontario. The drumlins are oriented in the 
direction of ice movement and are composed of unstratified and very 
compact till.^ 

The two glacial advances of Wisconsin time were separated by a 
rather short interval of deglaciation, and the readvance in the second 
of the two stages was along slightly different lines, so that the relative 
size and relations of the ice lobes appear to have undergone consider- 

1 Frank Leverett, Comparison of North American and European Glacial Deposits, Zeitsch. 
f. Gletscherkunde, Berlin, vol. 4, 1910, p. 279. 

- For discussion of drumlins or, more properly, rocdrumlins, formed out of shale and earlier 
till deposits in Menominee County, Michigan, and that drumlins are forms of aggradation in 
some cases and of degradation in others, see I. C. Russell, The Surface Geology of Portions of 
Menominee, Dickinson, and Iron Counties, Michigan, Rept. Geol. Surv. of Mich, for igo6, and 
H. L. Fairchild, Drumlins of Central Western New York, Bull. New York State Mus. No. iii, 
1907, pp. 393 et al. 



PRAIRIE PLAINS 469 

able change, and the moraines of the later stage cross those of the 
earlier at distinct angles, as at some points on Long Island (p, 470). 
The drift sheet of the later of the two stages is characterized by enormous 
terminal moraines, great bowlder belts, and an unusual development 
of kames, eskers, drumlins, outwash plains, valley trains, etc., all formed 
in such a manner as to show the disposal of the ice in the form of great 
lobes which in turn reflect the influence of the basins in which they were 
formed. The late Wisconsin drift is in many notable instances thin 
and overlies the interglacial fluvial deposits as a thin veneer of till. 

Topographic, Drainage, and Soil Effects 
topography 

In the successive periods of glaciation the ice advanced over the up- 
lifted and dissected peneplain of the northern Prairie Plains described 
in the preceding pages. In places it increased the relief by irregular 
deposition on a flat plain, in other places it decreased it by deposition 
in the valleys of a dissected plain. Had the country been mountainous 
an overriding ice sheet would not have produced till plains of such topo- 
graphic uniformity and continuity. The present reUef is therefore a 
function not only of glacial but also of preglacial topographic form. 

The topographic and drainage effects of the successive ice invasions 
are of the first magnitude in the region in which they occur, while the 
distribution of the soils is almost everywhere related to the material 
which the ice laid down or which the draining streams swept forward in 
the region immediately beyond that covered by the ice. The southern 
limit of ice advance is indicated upon the map, Plate , but it must 
not be thought that a single vast sheet of ice at any one time occupied 
the entire region north of the line indicating the limit of glaciation. 
There were in all at least six ice sheets which swept from the north at as 
many different times, from two of the three recognized centers of ice 
accumulation. The deposits produced by the successive ice invasions 
occur as distinct drift sheets between which, in intervals of deglaciation, 
soils and beds of peat and marl were formed (p. 467). In addition to 
these lines of demarcation between successive till sheets there are differ- 
ences among the sheets themselves; they vary in extent and physical 
constitution in a marked way. The lines of flow in successive invasions 
of ice were in many cases far from coincident, so that ice fields in some 
places fell short of earlier ones and in other places exceeded them. 

Another important feature is the existence of pronounced morainic 
ridges along the fronts of some of the till sheets, although this is not a 



47° 



FOREST PHYSIOGRAPHY 



constant feature, since a wide stretch of country in Illinois, Kansas, and 
Iowa is marked by the absence of a terminal moraine. Where the 
moraines are present it is noteworthy that the earlier ones have been 
very extensively eroded, so that many irregularities found upon the later 
moraines are wanting in the earlier. A typical occurrence is found in 
southern Illinois east of St. Louis, where practically all the kettle holes 
and minor depressions of the Illinoian moraine have been either filled up, 
or drained by the cutting down of their outlets, or both, while the detailed 
irregularities of the slopes of the hills and ridges have been so completely 
smoothed and rounded as to appear to a certain extent artificial. This 
group of qualities is in marked contrast to the nurnerous sags, depres- 
sions, kettle holes with lakes or swamps on their floors, and the extreme 
rugosity of moraines formed during the last (Wisconsin) ice advance. 



TERMINAL MORAINES AND TILL SHEETS 

The terminal moraines marking the margin of the last Wisconsin 
invasion are pronounced features of the landscape and often rise from 

loo to 200 feet above the sur- 
rounding surface. They may be 
traced almost continuously west- 
ward from Long Island to and 
beyond the Great Lakes. Not all 
the ice invasions of previous gla- 
cial epochs resulted in the devel- 
opment of pronounced terminal 
moraines. Some of the till sheets 
have distinct marginal ridges, 
while others are marked by mere 
swells of thicker drift at the mar- 
gins, and still others have very 
thin edges. 

The marginal deposits of the 
Wisconsin drift are in the form of 
bold terminal and interlobate 
moraines of such topographic 
importance that they have served to modify or to form entirely the 
divides between the smaller rivers. They fill a number of preexisting 
river channels and deflect many of the small streams and even many 
larger ones from their former courses. 

The concentric trend of the morainic ridges is to be ascribed to the 




Fig. 177. — The four drift sheets of Wisconsin. (Weid- 
man, Wise. Geol. Surv.) 



PRAIRIE PLAINS 



471 



lobate character of the ice margin, a feature imposed upon the conti- 
nental ice sheet by the irregularities of the topography which it covered. 
The depressions appear to have been lines of maximum flow, and in the 




Fig. 178. — Distribution of glacial moraines and direction of ice movement In southern Michigan and 
northern Ohio and Indiana. (Russell and Leverett, U. S. Geol. Surv.) 

Great Lake region this resulted in the strongly looped quality of the 
morainic systems as shown in Fig. 178. 

The extent to which drift deposits dominate the glacial topography 
is further indicated by the fact that the present divide between the 
Great Lakes or St. Lawrence drainage and the Mississippi drainage is 



472 



FOREST PHYSIOGRAPHY 



determined very largely by moraines and thick drift deposits. The 
drift is heaped up in greatest amounts at the ends and along the sides 
of the Great Lake basins where it was accumulated on the margins of 
tongues or lobes of ice that once occupied the basins. Such modifi- 
cation of not only the drainage but also the topography and the soils 
is clearly indicated by the nature of the drift covering in the south- 




Fig. 179. — Generalized glacial map of northern Illinois. (Barrows, Bull. 15, 111. Geol. Surv. 



ern peninsula of Michigan, northwestern Ohio, northern Indiana, and 
northeastern Illinois. The till deposits here attain their greatest 
thickness. The southern peninsula of Michigan is quite remarkable in 
this respect since the geographic position and relations of the Great 
Lake basins determined a maximum convergence of the ice lobes of 
this district. The northern half of the peninsula has a drift cover 
from 700 to 800 feet thick; the surface rises in places to looo or 



PRAIRIE PLAINS 



473 



iioo feet above the surface of the lakes; there seems to be no 
rock more than 250 feet above the lakes. ^ It has been estimated 
that the entire southern pen- 
insula of Michigan has an aver- 
age of about 300 feet of drift. 
The drift cover in the adjoining 
states on the south is about 100 
feet thick. These heavy glacial 
deposits do not consist of a single 
sheet, but embrace three, and in 
places four, distinct drift sheets 
which are the products of repeated 
glaciations at widely separated in- 
tervals. The upper surfaces of 
the older sheets are marked by 
beds of peat and river and lake 
deposits containing remains of 
life forms similar to those now 
e.xisting in the region, an indica- 
tion of a temperate interglacial climate not markedly unlike the climate 
of to-day. 

Farther west, as on the plains of eastern North Dakota, are many 




Fig. iSo. — Positions of the Wisconsin ice lobes about 
the Driftless Area. (Weidman, Wise. Gaol, Surv.) 




Fig. 181. — Relations of the drift sheets of Iowa and northern Illinois, i, Kansan; 2, Illinoian; 3, lowan; 
4, Early Wisconsin; 5, Late Wisconsin; 6, Driftless area; 7, course of the Mississippi River during the 
Illinoian glacial epoch. (After Leverett, U. S. Geol. Surv., and Calvin, Iowa Geol. Surv.) 



1 W. F. Cooper, Water-Supply Paper U. S. Geol. Surv. No. 182, 1908, Plate II. 



474 



FOREST PHYSIOGRAPHY 



surface features which also show the characteristic effects of glaciation. 
The country is here for the most part level, but it also presents long 
rolHng slopes rising from 300 to Soo feet above broad valleys. The 
most important topographic elements are massive ridges or mesas due to 

preglacial erosion. The mesas 
are in many instances bordered or 
crowned by long morainic ridges 
representing halts in the glacial 
advance or retreat. The morainic 
material is derived chiefly from the 
underlying shales (Cretaceous), 
and is a compact clay which 
also contains erratic fragments 
and bowlders of crystalline rock 
derived from northerly localities. 
The upper 5 to 10 feet of till has 
been oxidized to a light yellow 
color. The intermorainic tracts 
consist of rolling plains of till from 
a fraction of an inch to a hundred 
feet thick or of more level plains 
due to alluviation on the floors 
of glacial lakes. A typical in- 
stance of lake-bed topography is 
found in the upper James River 

- Southern limit of the Pleistocene ice sheet ^^d the Vallcy of the Red Rivcr.^ 
and distribution of moraines oE the Dakota glacial . , ,. . , 

(Wiiiard, u. s. PostglaciaJ Stream dissection has 
further diversified the topography, 
the Missouri River having cut a trench several hundred feet deep whose 
sides are for the most part steep. 

DRAINAGE MODIFICATIONS 

One of the interesting effects of glaciation was the diversion of streams 
from northward to southward courses; an instance of this is the Mis- 
sissippi in the southwestern corner of the Driftless Area below Dubuque. 
The valley maintains an even width of ij miles for about 12 miles, 
then widens gradually, and in a stretch of about 60 miles its width in- 
creases, except for a slight local contraction near the mouth of the 
Wisconsin River, and finally becomes 3! miles. This decided widening 
of a low-gradient valley upstream suggests that in preglacial time the 
valley was occupied by a northward-flowing river. 

> J. E. Todd, Aberdeen-Redfield Folio U. S. Geol. Surv. No. 165, igog, pp. 7 et al. 




lobe, North and South Dakota 
Geol. Surv.) 



PRAtRIE PLAINS 



475 



Other cases of stream diversions are discussed in connection with the 
Appalachian Plateaus, page 685, the Great Plains, page 405, and the 
Connecticut Valley, page 638. 

More general and quite as con- 
spicuous are the influences of 
glaciation upon the drainage sys- 
tems laid out upon the surfaces 
of the various till sheets or dis- 
posed along their margins. The 
Ohio and the Missouri have 
courses in marked sympathy with 
the glaciated tract, as if they had 
been pushed bodily out of pre- 
glacial courses, and such indeed is 
the case at many points on both 
streams. The Ohio in particular 
exhibits a valley whose most strik- 
ing characteristics are open- broad 
stretches alternating with rock- 
walled gorges which closely con- 
fine the stream; and abandoned 
channel stretches are exhibited at 
many points. Many less con- 
spicuous illustrations of stream diversions along the border of the 
glaciated country have been discovered.^ 

Within the borders of the till sheets influences no less striking are 
found. The moraine crests are the chief minor divides of the glaciated 
country and in many cases they are also the major divides. Number- 
less tributaries starting on the slopes of moraines are gathered into trunk 
streams which flow for long distances along the margin of a moraine or 
between parallel moraines before finding an outlet across one or the 
other of the moraines into a transverse stream (pp. 471 and 479). 
Stream courses within the morainic belts are characteristically irregular 
and marked by many lake-like expansions alternating with steep 
stretches and often by falls and rapids of great economic value. These 
conditions are in sharp contrast to the regular drainage lines and the 
general absence of lakes and waterfalls in the streams draining the 
smooth outwash plains that in many cases front the moraines. 




Fig. 18 



- Old and new channels of the Mississippi 
at the upper rapids, Fulton, 111. 



1 Frank Leverett, The Illinois Glacial Lobe, Mon. U. S. Geol. Surv., vol. 38, li 
103 et al. 



), pp. 102- 



476 



FOREST PHYSIOGRAPHY 




The preglacial drainage of the Great Lake region 
was probably very unlike the drainage of to-day, 
for borings along the line of the buried channel 
that runs across Michigan from Saginaw Bay to 
Lake Michigan indicate a fall toward the south- 
west and also a widening of the channel in that 
direction. Similar deep borings in western In- 
diana between the head of Lake Michigan and 
the Wabash show a lower rock floor than any yet 
discovered across Illinois, and suggest a preglacial 
drainage to the southward toward the Wabash 
and Ohio.' It seems probable that there was a 
divide on the line of the present St. Lawrence 
below Lake Ontario where the river now flows 
among the Thousand Islands from which the 
drainage was southwestward. 

The outlines of all the lake basins have been 
notably affected by the deposition of drift in part 
on their margins, in part on their floors. Near 
the mouth of the Cuyahoga River at Cleveland 
the drift extends more than 470 feet below lake 
level and to within 100 feet of sea level, while 
the greatest depth of water of Lake Erie is but 
210 feet and the average depth only about^yo 
feet. These figures indicate a very notable 
modification of the western end of Lake Erie 
by the deposition of till, and such modification 
when brought about by a large ice mass must in- 
evitably be associated with very notable changes 
in the preglacial drainage. 

Fig. 184 is a profile across Lake Michigan, 
showing the extent to which drift forms a barrier 
to the lake waters at the present time. 



LAKE PLAINS 

The so-called Lake Plains of the Great Lake 
region are special features of the Prairie Plains 
province. They have an aggregate extent of several thousand square 
miles and form long narrow strips of smooth country bordering the 

1 Frank Leverett, Outline of History of the Great Lakes, 12th Rept. Mich. Acad. Sci., 1910, 
p. 22. 



PRAIRIE PLAINS 477 

Great Lakes in sharp contrast to the rough morainic country about 
them. Many portions of them have low gradients, smooth sur- 
faces, regular consequent drainage, fine soils, and extensive marshy 
tracts that remind one strongly of portions of the Atlantic and Gulf 
Coastal Plain. They have an aggregate extent of several thousand 
square miles, but this is far less than the area usually assigned to them. 
There is no doubt that their extent as represented on Powell's physio- 
graphic map of the United States ^ is greatly exaggerated. For the most 
part they are closely confined to the borders of the Great Lakes. In 
places they extend inland for 50 or 60 miles, but such breadths are excep- 
tional. Commonly their width is under 20 or 30 miles. 

The Lake Plains lie between morainic ridges and the lake shores. The 
morainic ridges are concentric with respect to the existing lakes since 
the lake basins were lines of movement of the glacial lobes along whose 
margins the moraines were developed. The lakeward slope of the inner- 
most moraine formed the border of the lake and against this slope beach 
ridges and wave-cut platforms were developed in many cases. Where 
the innermost moraine was feebly developed or lower than its outer 
neighbors it did not determine the lake border. Furthermore, the lakes 
once lying over the lake plains were constantly changing in level and hence 
in outline. Shore lines are found between the outermost abandoned 
shore line and the present lake shores. These were developed not upon 
moraines but upon smooth lake floors uncovered by the retreat of the 
lake waters as they fell to lower levels. 

The shallowness of the glacial-marginal lakes and the gradual move- 
ments of the shore zone of maximum wave action over the entire lake 
floor exercised a smoothing effect upon the lake bottom elevations. 
These lake bottoms, now exposed, in many cases exhibit a topography 
varied only by recent stream channels opened in them and by shallow 
depressions filled with small swamps, ponds, and lakes. 

PROGLACIAL LAKES" 

It was known even to the first settlers that lakes formerly occupied 
not only the present lake basins but also the bordering lands thus over- 
lying the present lake plains and forming the prominent beaches developed 

1 J. W. Powell, Physiographic Regions of the United States, in Physiography of the United 
States, Nat. Geog. Mon.. 1896, pp. 98-99. 

2 Whittlesey and Warren, The Great Ice Dams of Lakes Maumee, Am. GeoL, vol. 24, 
1899, pp. 6-38. See Frank Leverett, The Glacial Formations and Drainage Features of the 
Erie and Ohio Basins, Mon. U. S. Geol. Surv., vol. 41, 1902, for an excellent brief historical 
review of the problems of the abandoned shore lines of the Great Lake region as well as for a 
compact summary of the physical changes and a good working bibliography. See also J. W. 



478 FOREST PHYSIOGRAPHY 

in numbers about the existing lakes at both high and low levels. Many 
of the beaches once served as trails for the Indians. Their level, dry, 
and moderately straight courses are also ideal for modern purposes. 
They are generally known as " ridge roads " and are fairly common in 
the southern part of the Great Lake region. 

It was early demonstrated^ that the lakes owed their origin to ice 
dams now extinct, and that the water impounded in front of the ice 
dams rose to the level of the lowest point on the rims of the enclosing 
basins and then overflowed into valleys draining to the sea. The ice 
dams were nothing more or less than the frontal lobes of the retreating 
continental ice cap of late glacial time. 

To understand these relations one should conceive of a great continen- 
tal ice sheet whose front was being melted back from a southern limit, 
Plate IV, so that it finally lay on the northern side of the great divide 
which separates the St. Lawrence drainage system from the Mississippi 
and Atlantic drainage. From the pattern of the terminal moraines 
shown in Figs. 178 and 182, the border of the continental ice sheet is 
known to have been lobate. Each lake basin as well as each subsidiary 
bay, such as Green Bay or Saginaw Bay, was occupied by an individual 
lobe of ice connected at the north and east with the main ice sheet. 

In front of each ice lobe and in the southwestern and western portions 
of the St. Lawrence basin there eventually formed a glacial-marginal or 
proglaciai lake which was at first crescent shaped, but with continued 
retreat of the ice its shape would be modified by the general outlines of 
that part of the basin that was not occupied by the ice lobe. It is also 
clear that the lake water could not discharge over the thick ice sheet or 
under it, but must have discharged along its front or across the divides 
on the distal margins of the basin. Lake Chicago is the name applied 
to the crescent-shaped lake that formed in front of the Lake Michigan 
lobe and discharged through the Desplaines-Illinois rivers. In a simi- 
lar way Lake Maumee was formed in front of the Erie lobe and dis- 

Goldthwait, The Abandoned Shore Lines of Eastern Wisconsin, Bull. Wisconsin Geol. and 
Nat. Hist. Surv. No. 17, 1907, for historical data of interest and for unusually accurate and 
detailed studies of abandoned shore lines in Wisconsin. More recently observation has been 
extended into Canada by Taylor and Goldthwait and the conclusions based on studies in the 
United States correlated with the observations of Coleman and others on the Canadian Geo- 
logical Survey. The results of the refined studies of recent years point conclusively to the 
truth of Spencer's early contentions that the deforming movement of the region was difier- 
ential and greater toward the north, a conclusion long neglected outright or regarded with 
undeserved skepticism chiefly because of the author's retention of the overthrown hypothesis 
of marine submergence. 

I G. K. Gilbert, On Certain Glacial and Postglacial Phenomena of the Maumee Valley, 
Am. Jour. Sci., vol. i, 3d ser., 1871, pp. 339-345. 



PRAIRIE PLAINS 



479 






a —-^fir-^ 






[/ iUi 





Fig. 185. — Drainage history of the southern Great Lake district. A, position of glacial lakes before 
lakes were formed; B, beginning of Lake Chicago; C, D, E, F, later stages in retreat of ice and expansion 
of proglacial lakes; G, retreat of ice from Mohawk valley and discharge of proglacial lakes down the 
Hudson; H, present drainage. 



charged through what is now the valley of the Maumee into the Wabash 
past Fort Wayne. Lake Duluth was formed in front of the Superior 
lobe and discharged down the Chippewa to the foot of Lake Pepin in 
the Mississippi Valley. 
On the borders of the glacial-marginal lakes, deltas, shore lines, and 



48o 



FOREST PHYSIOGRAPHY 



offshore deposits were formed, and on the bottoms, muds, sand, and 
silts were deposited. One side of each lake had a temporary shore 







Fig. 1S5. Continued. 



line — the unstable ice wall which marked the front of each glacial 
lobe. It must also be noted that this ice wall was not fixed. Some- 
times it advanced slightly, overriding the beaches that had been formed 
by the lake water in front of it; sometimes it remained stationary long 
enough to accumulate a water-laid moraine on the lake floor and a land- 



PRAIRIE PLAINS 481 

kid moraine on the adjacent land surface; but the net result of all 
the changes of ice front was a gradual retreat northeastward. Asso- 
ciated with this retreat was the gradual extension of the glacial-marginal 
lake waters and to a certain degree their coalescence along the ice 
front, as in the case of the water bodies at the heads of Saginaw Bay 
and Lake Erie, Fig. 1S5-E. Numerous changes in outlet also took 
place, among which only the principal changes are noted below. The 
principle which controlled these changes is, that with each marked re- 
treat of the ice lower surfaces were exposed which would have different 
relations to each other with respect to elevation. 

Thus Lake Maiimee for a time discharged into Lake Chicago by way of the Saginaw basin 
and the Grand River Valley. Lakes Michigan and Huron for a time discharged through 
Georgian Bay and the Trent Valley into Lake Iroquois (Ontario), and a still later and lower 
outlet was afforded through the Ottawa River Valley on the uncovering of this drainage way 
through the further retreat of the ice. This stage is known as the Nipissing stage. 

At this time Lake Erie drained across the Niagara escarpment and Lakes Huron, Michigan, 
and Superior drained eastward through the Ottawa Valley to the St. Lawrence. The small 
amount of water discharging over Niagara Falls during this period resulted in the production 
of a very narrow gorge, but the gradual tilting of the land toward the southwest caused the 
Ottawa outlet to be abandoned and the low col south of Port Huron to be occupied by a new 
drainage channel marking the outlet of these three great lakes into Lake St. Clair and Lake 
Erie. Associated with this change in outlet and the greater discharge of water over Niagara 
Falls was the widening and still more marked deepening of the gorge between the whirlpool and 
the Suspension Bridge, changes which are conceived to have occurred in the last 5000 years, 
judging by the present rate of retreat of the falls. The St. Clair outlet of Lake Huron is thus 
seen to be a very recent geologic event, as may be seen clearly also by the youthful character 
of the valley of that river and the recent formation of a feature which is anomalous in physical 
geography — the delta at the head of Lake St. Clair, formed by the short St. Clair River. A 
river draining a lake is singularly free from sediment at the intake, and it might be expected 
that a very small delta or none at all would be formed at the mouth of so short a stream as the 
St. Clair. Instead, the recent occupation of the valley of the St. Clair by the St. Clair River 
has caused very rapid channel cutting that is still in progress, an action that is reflected in 
the large delta at the head of Lake St. Clair. Tending toward the same result are the shore 
currents of Lake Huron, which deliver a large amount of beach sand to the intake of the 
St. Clair.i 

The former small size of the lake in the Erie basin and the fact that it did not then cover 
the western part of the basin are established by the deeply submerged lower courses of the 
streams in the western part of the basin, especially that of Sandusky River, which has been 
traced entirely across the bed of Sandusky Bay. More recent changes of water level at this 
end of the basin are shown by the submerged level of the valleys discharging into Lake Erie 
and the submerged stalactites in the caves of Put-in Bay Island at the western end of the lake. 

During still later stages of their history the lakes discharged through the Mohawk and 
down the Hudson. The great sand plain at Albany and Troy was the delta of this large- 
volume, temporary stream. Through the later uncovering of the St. Lawrence Valley by con- 
tinued ice melting a lower point of discharge was offered to the lake waters and the Mohawk 
channel abandoned. The present Mohawk River occupies but a small portion of the ancient 
glacial channelway. 

The earliest formation of glacial-marginal lakes in the Lake Superior drainage basin appears 
to have been in the area now drained by the St. Louis River, where the waters were ponded at 

1 L. J. Cole, The St. Clair Delta, Mich. Geol. Surv., 1005. 



482 



FOREST PHYSIOGRAPHY 



93 


92 


91 


90 


89 88 »T 


86 


85 84 








/ ■-••S\ 






-4-4- 


J , 






-r"a .J 






. 


J c ^ 

\r 


*• -N' A D A 








:;-""v--; 


1 


V N I 
S T A 


..•■■■ 


; ...- 




..,•■■;.;' ...-. ;■•■' 


:::::> 




— I — 




iUilMisMi 


*^_ 






^^K-^W|] 


— ®>^ — ^ 


-^ 


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r 


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93 92 91 90 89 



Fig. 186. — Superior ice lake and glacial marginal Lake Duluth. (Leverett.) 



91 90 89 




93 92 .91 90 



85 84 



Fig. 187. — Lake Duluth at its greatest extent and the contemporary ice border. (Leverett.) 



PRAIRIE PLAINS 483 

an altitude of about 700 feet above Lake Superior, Fig. 186. To this small transient body of 
water the name of Lake Upham has been given. The fringing ice later afforded a lower 
passage about 530 feet above Lake Superior, and the resulting lake with outlines quite different 
from those of Lake Upham and with a different line of discharge has been called Lake St. 
Louis. Still further retreat of the ice border resulted in the formation of a lower lake about 
500 feet above Lake Superior, known as Lake Nemadji, which discharged a large volume of 
water (from Kettle River Valley) into the St. Croix. These lakes lie quite beyond the border 
of Lake Superior, and well above it. The name Lake Duluth has been given to the extremely 
large body of water draining southward from the head of Brule River into the St. Croix 
River and occupying a large portion of the area now occupied by Lake Superior. The high- 
est shore line of Lake Duluth at the western end of the basin shows a marked rise toward 
the northeast. At Duluth it is 465 feet above Lake Superior, while at Calumet on the 
Keeweenaw peninsula it is 702 feet above it. The rise of 237 feet seems to be largely due to 
differential uplift, though, as in the case of all the other deformed beaches of the region, a 
small portion is referable to ice attraction, though this will account for but 37 of the 237 feet 
and was effective only within a few miles of the ice border. The difference of 200 feet seems 
explainable only on the ground of differential movements since the formation of the earlier 
shore lines. 

During and since the retreat of the ice, tilting of the Great Lake region 
has been in progress. Elevated and now tilted and abandoned shore 
lines occur in numbers about the lakes of the Great Lake region. In 
places they are very numerous, as about the head of Lake Superior, 
where may be counted more than 30 distinct strand lines, representing 
as many successive lowerings of water level through the vicissitudes 
associated with the melting of the ice and the uncovering of lower and 
lower outlets. The beaches all rise in altitude toward the northeast, 
with a slightly increasing divergence in that direction, showing that the 
uplift of the land which gave the shore lines their present attitude was 
differential and greater toward the north; also that the tilting was not 
that of a simple plain but of a warped surface.^ 

With a view to determining the degree of stability of the Great Lake 
region, Gilbert compared the elevations of certain bench marks as 
determined in 1876 and again in 1896. After a careful elimination of 
all irregularities of lake levels due to wind, tide, etc., it was found that 
there was a small but definite increase in height in a northerly direc- 
tion, and that the tilting is greatest in a direction south 27° west, and 
is at the rate of 0.42 foot per 100 miles per century. 

The prolonged tilting of the Great Lake region is also shown by the 
drowned lake shores on the west side of the lower peninsula of Michi- 
gan, where many of the rivers discharge into pouch-shaped lakes sepa- 
rated from the main lake by long slender sand bars, as the Black River, 
the Muskegon, the Pentwater, and in a similar way at the western end 
of Lake Erie, the Maumee, the Rouge, the Raisin, and the Huron. In 

> J. W. Spencer, Deformation of the Algonkian Beach and Birth of Lake Huron, Am. Jour. 
Sci., vol. 141, 1891, pp. 12-21. 



484 



FOREST PHYSIOGRAPHY 




Fig. i88. — Isobasic map of the Algonkian aad Iroquois beaches, showing the broader features of 
warping. Numbers indicate elevations of raised beaches above the sea. (Goldthwait.) 



.^0-DSOJf ? 



.^- 




^.-7- i: 



Fig. 189. — Map of e.\tinct Lake Agassiz and other glacial lakes. (Upham 
U. S. Geol. Surv.) 



PRAIRIE PLAINS 485 

contrast to these features of shore lines of subsidence are the features 
indicating elevation on the shore lines of the eastern side of Lake Huron 
at Kincardine and Goderich, Ontario, where the rising land keeps the 
lake always at work on new levels, and till, bowlders, cobblestones, and. 
pebbles are everywhere in evidence. The near-shore bottom is stony 
and the stream discharging into Lake Huron at Kincardine has a stony 
bed, caving banks, and impetuous How, indicating uplift and constantly 
renewed energies.^ If the tilting continues at the present rate, the water 
of Lake Michigan will ultimately discharge across the low divide that 
separates the lake from the Desplaines Valley. Its channel will then be 
reoccupied and Niagara will become dry. It has been calculated that 
this change would take place naturally in from 5000 to 10,000 years; but 
man has anticipated the change by cutting a drainage canal for diverting 
the sewage of Chicago from Lake Michigan to the Illinois River — a pro- 
ject enforced by the urgent need of a pure supply of lake water for a 
concentrated population. The old outlet channels of the glacial-mar- 
ginal lakes are among the most distinctive topographic and drainage 
features of the entire region. At the present time the Desplaines has a 
wide steep-walled valley with a fiat marshy floor thronged with lakes, 
bayous, irregular depressions, and stream channels. The present valley 
was the channel of the outlet of Lake Chicago, and the irregularities of 
the present valley are nothing more than the irregularities normal to 
the channel bottom of a large stream. 

In the Red River Valley similar drainage changes of equal importance 
took place. Upon retreating gradually from the Lake Winnipeg-Red 
River Valley the Keewatin glacier was met by the gradually advancing 
Laurentide glacier, and the union of the two caused a ponding of the 
waters between their fronts, which produced glacial-marginal Lake Agas- 
siz. The lake waters rose until they overflowed southward into the 
valley of the Mississippi and then gradually declined. The Laurentide 
glacier advanced to the western shore of Lake Winnipeg; this extreme 
advance was some time after the advance and retreat of the Keewatin 
glacier, and between the two till sheets stratified deposits occur near 
the mouth and on the banks of the Saskatchewan River. The large 
areas of flat fertile soil in the Red River Valley are largely lacustrine 
deposits — silts and clays formed on the floor of the ancient glacial- 
marginal lake and now exposed by the extinction of the lake, Fig. 189. 

1 Mark Jefferson, The Geography of Lake Huron at Kincardine, Ontario, Jour. Geog., 
vol. 2, 1903, pp. 144-155. 



486 FOREST PHYSIOGRAPHY 

Soils of the Glaciated Country 

Each type of glacial topography in a glaciated country has not only 
its own distinctive slopes but also its distinctive soils. A map of the 
glacial forms of a region is therefore to a large extent a soil map of the 
region. Terminal moraines are noted for stony till, outwash plains 
for their porous, gravelly, stratified, alluvial nature, eskers for their 
cobbly material, and kettle and kame topography is marked by sandy hill- 
slopes and undrained hollows with soils largely of organic origin. These 
are not hard and fast criteria but they are in general true. Exceptions 
to the rule are the sandy moraines near the Great Lakes, the stony out- 
wash where a late glacial readvance of the ice veneered the surface with 
a thin ground moraine, etc. Between the concentric terminal moraines 
formed during the retreatal stages of glaciation one finds in, many cases 
extensive tracts of sub-level land formed of till, the so-called ground 
moraine. These tracts are in many cases poorly drained and their soils- 
therefore have a high content of organic material. They form the 
flattest and richest parts of Illinois and Indiana, and lie in the so-called 
"corn belt" of these and other states. 

The unweathered condition of the soil minerals throughout the most 
recently glaciated area insures prolonged fertility of the soil. The older 
glacial deposits have been weathered to an important degree. Both the 
Kansan and lUinoian drift sheets. Fig. i8i, have been greatly leached and 
large portions of their original calcareous content removed. The Wis- 
consin drift is fresh and unaltered, one of its distinguishing features. It 
is also noteworthy that the older drift sheets have a smaller proportion 
of organic matter in their soils than is the case with the youngest or 
Wisconsin sheet. Since the deposition of the Wisconsin drift there has. 
accumulated large quantities of organic material along the shores of the 
small lakes and ponds, indeed some of the water bodies have disappeared 
through the filling of the basins by sediments, plant remains, and the cut- 
ting down of the outlets. The older till sheets have been so extensively 
eroded, on the other hand, that the accumulated organic remains in the 
small basins have been largely removed and the soils to that extent 
impoverished. Corresponding contrasts are exhibited in the value of 
the soil products, the density of population, and the natural vegetation.^ 

Over the old lake bottoms the soil varies considerably from place to 
place according to (i) the nature of the underlying glacial deposits, 
(2) proximity to a well-defined strand line, (3) character of the post- 

1 Frank Leverett, The Illinois Glacial Lobe, Men. U. S. Geol. Surv., vol. 38, i8gg, pp. 734- 
736 at al; also An Instance of Geographical Control upon Human Affairs, Geog. Jour. (London), 
voL 24, 1904. 



PRAIRIE PLAINS 487 

glacial drainage, etc. In some places the soil is a fine silt, loam, or clay, 
and is free from stones and bowlders and very fertile. In other locali- 
ties it is marked by the presence of stones and bowlders, as where a 
beach was formed against the slopes of a rocky moraine, although 
for the most part the beaches are composed of sand and gravel. The 
poorly drained portions of the lake plains are in the aggregate of con- 
siderable extent and are marked by post-lake accumulations of vege- 
tation in sufficient amounts to form a surface layer of peat or muck of 
great fertility when properly aerated by drainage. Many of the most 
productive of the market gardens that supply the cities of Port Huron, 
De roit, and Chicago are formed upon these extensive, poorly drained 
muck swamps. 

Some of the beach levels are so warm on account of their porous 
soils and excellent natural drainage as to be ideal sites for vineyards 
and orchards, a feature well marked in western New York south of 
Lake Ontario. The lake plains on the eastern side of Lake Michigan 
and Lake Huron are noted for their large production of fruit, but this 
development is dependent to a greater degree upon climate than upon 
soil, for the Great Lakes are exceptionally large bodies of water and 
mitigate both the heat of summer and the cold of winter. The east- 
ward or leeward side is favored by sufficiently moderate winter tem- 
peratures to permit the development of peach, plum, cherry, and apple 
orchards in great numbers. 

In the northern part of the southern peninsula of Michigan the 
glacial deposits are exceptionally sandy and infertile, and large tracts, 
aggregating nearly one-sixth of the state, are known as the "pine bar- 
rens." Six million acres of these lands have been thrown on the delin- 
quent tax hst and are a burden to the people. Formerly they were 
covered with magnificent forests of white pine. These were so thor- 
oughly cut down, the surface so extensively and repeatedly burned, and 
young growth and humus so devastated, that great areas have been 
rendered all but worthless, 

Sandy tracts are also found along the lake margins and in some cases, 
as at the southern end of Lake Michigan, appear to be due to the fact 
that beach and dune material, formed on the borders of the interglacial 
Great Lakes, was reworked and redeposited during the last (Wisconsin) 
glaciation. Further modification has resulted from wind action, the light 
sands having been blown into dunes some of which attain an enormous 
size. "Creeping Joe" on the eastern shore of Lake Michigan, near 
Muskegon, is one of the largest dunes in the world, with a relative alti- 
tude of several hundred feet. The dunes are most numerous on the 



488 FOREST PHYSIOGRAPHY 

eastern shores of the lakes, as on the eastern shores of Lake Michigan 
and Lake Huron, where sandy deposits are exposed to the full force of 
the wind sweeping in from the lakes. 

LOESS DEPOSITS 

The student of soils must take account of an important deposit in the 
Mississippi Valley related to glaciation and known as loess. The loess 
deposit of the Prairie Plains extends westward from a point east of the 
Mississippi and has its greatest development in Illinois, Iowa, Nebraska, 
and the states to the southeast. The distribution of loess is one of its 
most important features. It is thick about the borders of the area occu- 
pied by the lowan ice sheet, but thins out on interstream areas when 
traced away from this border tract, though it retains its thickness along 
the larger valleys.^ It follows the Mississippi nearly to the Gulf, and is 
particularly well developed along this stream and the Missouri. It is 
habitually found on blufTs immediately overlooking the valleys, and in 
this position has more than average thickness and coarseness of grain, 
becoming thinner and finer at a distance from the valley margin." The 
northernmost limit of the loess in the central part of the United States 
is about 35 miles below St. Paul, Minnesota. In central and eastern 
Illinois and south-central Ohio it passes under the Wisconsin drift. In 
the Mississippi basin the loess is rarely over a score or two of feet in 
thickness, though exceptional thicknesses of nearly loo feet have been 
noted. It is composed of angular undecomposed particles of calcite, 
dolomite, feldspar, mica, and a certain number of rarer minerals. It is 
generally light brown in color and is a variety of silt intermediate in size 
of grain between the finest sand and clay. Stones are generally absent 
except at its base. On erosion it often exposes vertical faces for long 
periods. It is markedly porous, owing in part to vertical tubes usually 
found in it and supposedly due to root action.^ 

The loess is preponderatingly on the east sides of the main rivers, and 
this fact suggests the hypothesis of an eolian origin, which has perhaps 
more to commend it than the rival aqueous hypothesis. It appears 
that the loess is chiefly wind derived and that favorable opportunities 
"for its formation were afforded by the periodic flooding and drying up 
of the alluvial deposits along the streams of the region either in the in- 

1 Chamberlin and Salisbury, Geology, vol. 3, igo6, p. 407. 

2 Frank Leverett, Comparison of North American and European Glacial Deposits, Zeitsch. 
f. Gletscherkunde, Berlin, vol. 4, 1910, p. 297 £E. 

3 For an excellent discussion of the various phases of the loess problem, and for recent 
data of great consequence, see B. Shimek, Jour. Geo]., vol. 4, pp. 929-937, and various loess 
papers, Bulls. Lab. Nat. Hist., Univ. Iowa, 1904. 



PRAIRIE PLAINS 489 

terglacial period preceding the lowan glacial invasion or during the lowan 
invasion itself. The absence of fiuvio-glacial deposits in important 
amounts on the margin of the lowan till sheet would appear to favor 
the idea of a dry glacial stage, strange as this may seem. 

It is found that the loess is thicker on eastern or lee sides of ridges 
and prominent hills than on the windward sides, a feature that harmo- 
nizes with the thicker deposits on the east sides of the stream valleys 
in pointing to wind action as the chief factor in loess deposition. The 
diminishing amount of loess in an eastward direction suggests that a 
considerable part of the material was derived from the Great Plains 
east of the Rocky Mountains, where dust storms are frequent even 
to-day. 

That the loess was deposited in an interglacial period is supported by the fact that buried 
soil occurs between the loess and the glacial deposits, and appears to indicate a long period 
between the melting of the ice and the deposition of the loess. This view is strengthened by 
the finding of a molluscan fauna in the loess strikingly similar to the existing fauna, showing 
that the conditions which prevailed when the loess was forming were not greatly different from 
those now existing in the region.' 

The shells found in the loess are almost exclusively those of land species or such as frequent 
isolated ponds. There is a practical absence of forms that frequent rivers and lakes. Fossils 
of land mammals, chiefly in the forms of bones and teeth, have also been found. 

Tree Growth of the Prairies 

By definition a prairie is an extensive tract of land, level to gently 
rolling, without a timber cover. The definition includes the idea of a 
meadow or at least a grassy vegetation. The distinction between plain 
and prairie as the terms are actually employed in the United States is 
not sharply drawn, but in general they are considered to differ in two 
main respects. The prairie country is dotted with groves of trees and 
has a continuous grass cover or sod; the plains country is without timber 
except along the streams, on prominent elevations, and in places about 
springs; the grassy vegetation of the plains is disposed in clumps sepa- 
rated by bare spaces. A view in any direction on the typical prairies 
includes groves and bands of trees and even tracts of true forest. The 
phrase ''Prairie Plains" as here used means the whole great region in 
which patches of prairie occur and not merely the true prairie land 
exclusive of wooded tracts (see Plate I and Fig. 23). 

Since the whole prairie country lies in the belt of moderate to light 
rainfall between the semi-arid West and the humid East, Fig. 19, it fol- 
lows that there are great differences in the relative amounts of woodland 
and true prairie. On the east, north, and south the province borders 

1 See especially Proc. lowan Academy of Science, vol. 15, 1909, pp. 57-75. 



49° 



FOREST PHYSIOGRAPHY 



heavily forested tracts; on the west it borders an all but treeless region. 
In general the largest tracts of true prairie within the province are 
found toward the west in the direction of diminishing rainfall. Locally, 
however, there are extensive tracts well within the western border. 

South of Chicago, for example (Fig. 
190), is a large tract known as the 
Grand Prairie with a rainfall of 35 
inches a year. Extensive prairie 
tracts occur also in northern Indiana, 
southern Michigan, etc. 

On the north the Prairie Plains 
province is covered with the southern 
edge of the great pine and hemlock 
forests of the Lake Region. The in- 
dividual trees attain great size, espe- 
cially on the sandy glacial material 
south of the Straits of Mackinac in 
Michigan; the virgin growth of this 
district consisted of extensive stands 
of superb forest. Farther south is 
the zone of hardwoods with many 
outliers of the northern pine forests, 
especially where the land is either 
too wet or too dry. The sand}^, dry 
situations have a growth of pines; 
in the wettest situations are growths 
of cedar and hemlock. In the in- 
termediate situations are woodland 
and a true forest growth of mixed 
hardwoods. The occurrence of the 
hardwoods on the richest land is notable and in part explains why they 
were so extensively destroyed in clearing of land for agriculture. It 
is a common saying that the soil supporting a good growth of beech and 
maple forest is better than open prairie soil or land so wet that it must be 
drained before being cultivated. While the saying has a great deal of 
truth in it, it must also be noted that the peaty soils of low situations 
have a high fertility when they are properly drained and sweetened and 
are better than the upland soils for the production of many vegetable 
products. WTiat measure of truth the saying contained led the settlers 
rapidly to clear away the hardwood forests until now the supply of 
hardwood is greatly diminished and in urgent need of conservation. 




Fig. 190. — Original distribution of prairie and 
woodland in Illinois. (Barrows, 111. Geol. 
Surv., modified from Gerhard.) 



PRAIRIE PLAINS 491 

Many owners are beginning to realize the value of their wood lots and 
are no longer cutting them for fuel but for timber. 

The strongly marked topographic and drainage features of the heavily 
glaciated country about the Great Lakes have had an important control 
over the forests not only in the distribution of the forest flora but also 
in the development of the forest products. It is noteworthy that the 
steeper slopes of the terminal moraines are wooded because too steep 
for cultivation, just as bottom land and upland are in many places cleared 
of their original timber cover while the steep undercut river bluffs are 
allowed to remain tree-covered. The terminal moraines are not only 
rough, they are also stony and clayey; many miles of terminal moraine 
are composed of tough stony clay too difficult of cultivation to com- 
pete with better favored tracts of outwash and ground moraine in the 
intermorainic belt. Such tracts are commonly left wooded or used for 
pasture-land or for special crops such as flax and rye. It is also note- 
worthy that the steep slopes of drumlins in the glaciated country are 
commonly left in their original wooded condition. Some drumlins have 
narrow summits, others have broad rounded tops. In the latter case 
a farm may be located on the summit, in the former case the timber 
cover may be left undisturbed. In the same way the borders of marshy 
tracts and the floors of undrained depressions are covered with a growth 
of swamp vegetation including the swamp oaks and maples, buttonwood, 
elm, cedar, and other types. The aggregate of such land is large and 
with suitable improvement might be made to grow a steady supply of 
valuable timber. 

On the east the forests of the Prairie Plains grade off into the more or 
less continuous stands of the Appalachian region in the belt of heavier 
rainfall. On the south they merge into the pine forests of the Coastal 
Plain and on the west into the scattered hill and escarpment timber of 
the Edwards Plateau and its outliers in central Texas. Farther north, 
as shown in Fig. 23, long finger-like extensions of the Prairie Plains 
timber follow the stream valleys. For some distance this growth covers 
both bottom lands and valley slopes and bluffs; farther west it is con- 
fined to the bottom lands wholly and still farther w^est it is found only 
along the margins of the streams. 

The tree growth of the Prairies of Texas has such a close relation to 
the geology, water supply, and soils as to warrant a more detailed descrip- 
tion of its occurrence. The Prairie Plains are here but 100 miles wide 
and consist of two main subdivisions, — the Black Prairie on the east 
and the Grand Prairie on the west. The Black Prairie is developed 
upon a series of marls, sands, and limestones that dip gently east- 



492 ' FOREST PHYSIOGRAPHY 

ward. The marls have weathered into a uniform and very gently 
undulating type of topography terminated on the west by a low 
inward-facing escarpment that never exceeds a relative altitude of 200 
feet. It is known as the Black Prairie. West of the Black Prairie 
is the Grand Prairie, developed upon nearly horizontal limestones of 
great extent as a series of fiat structural plains terminated in succession 
on the coastal side by low inward-facing escarpments. The western 
border of the Grand Prairie is a pronounced escarpment wdth a lobate or 
crenulated outline that extends from Arkansas, west and south through 
Oklahoma and Texas, to the Rio Colorado, whence it curves about to 
the west and north and becomes the eastern escarpment of the Great 
Plains. 

The most important forest tracts of this region are the Western and 
Eastern Cross Timbers, two narrow forest belts developed upon the 
inner edge of the Grand Prairie and Black Prairie respectively. They 
are of peculiar interest since they form long narrow ribbons of forest 
in what is otherwise a prairie country. Both belts have been developed 
upon the outcrop of two sandy formations (Cretaceous). The open 
sandy soils not only permit thorough aeration, but also favor the rapid 
absorption of water during periods of rainfall, whereas the close-textured 
soils of the intervening prairies shed water to an exceptional degree and 
are too dry for tree growth. The limited rainfall of the district thus 
makes the porosity of the soil a determining factor in forest distribution. 
The Eastern Cross Timbers consist of a belt of timber whose extent is 
shown in Fig. 191. It has many outliers towards both the east and the 
west and like the Western Cross Timbers sends finger-like extensions up 
and down the stream-ways. Within the Cross Timbers are many local 
prairie tracts. The Western Cross Timbers are about 10 miles long and 
have about the same extent north and south as the Eastern Cross Timbers. 
The various irregularities of the belt in response to geologic changes and 
to relief are clearly indicated in Fig. 191. The western border of the 
Western Cross Timbers is the more indistinct since it merges into local 
forest tracts developed upon other sandy formations. Wherever compact 
marls and clays outcrop there is a marked absence of forest growth except 
in cases where the mesquite grows. In general the surface is without tree 
growth between and on either side of the Cross Timbers; it is here that 
the prairies of Texas have their most typical development.^ 

Among the effects of glaciation none is perhaps more directly inter- 
esting to the forester than the overwhelming effects of the continental 

1 R. T. Hill, Geography and Geology of the Black and Grand Prairies, Texas, 21st Ann. 
Rept. U. S. Geol. Surv., pt. 7, 1899-1900, pp. 65-85. 



PRAIRIE PLAINS 



493 




WESTERN LAMPASAS FT. WORTH EASTERN BLACK 

CROSS CUT PLAIJ< PRAIRIE CROSS PRAIRIE 

TIMBERS TIMBERS 



Fig. igi. — Cross Timbers of Texas. 

ice caps upon the forests whose regions they invaded.^ During the 
period of maximum development the ice had a most disastrous effect 

1 C. H. Merriam, The Geological Distribution of Life in North America with Special Refer- 
ence to the Mammalia, Proc. Biol. Soc. Washington, vol. 7, 1892, pp. 42 and flf. 



494 FOREST PHYSIOGRAPHY 

upon animals and plants, not only in the great area occupied by it, but 
far south of its actual border. As the ice advanced from the north, 
northern species were driven southward and more southerly species 
correspondingly displaced or exterminated. It appears that .the gradual 
southward movement of the cold zone greatly restricted the range of the 
plants, compressing them from north to south within very narrow limits. 
Perhaps the most interesting evidence of the strength of this hypothesis 
is the presence of colonies of Arctic species on isolated mountain summits 
in southerly latitudes where at a Ligh altitude abnormally low temper- 
atures exist similar to those which exist in their northern homes. Such 
colonies could not in many cases have reached their present position 
during existing climatic conditions; following the retreat of the ice at 
the close of the glacial period many boreal species were stranded on 
mountains where their survival was conditioned by their ability to 
migrate with a congenial climate. 

Driftless Area 

Lying well within the southern border of the general region once 
covered with glacial ice is a small district, Fig. 192, which has never 
suffered glaciation. It is called the Driftless Area. Its extent is about 
10,000 square miles and it lies in the states of Wisconsin, Illinois, Min- 
nesota, and Iowa, the greater part of it occurring in southwestern 
Wisconsin. The soil of the Driftless Area is residual, derived directly 
from the decay of the underlying rock. Like residual soils everywhere 
the surface detritus grades gradually into solid rock and there is not 
that sharp dividing line that is found between glacial or other over- 
placed soils and the rock surface. 

The surface of the Driftless Area is topographically mature and the 
drainage is well organized, without falls and rapids and lakes or 
sv/amps except within narrow limits and along the river bottoms. 
The aimless flow of streams developed upon the irregular topography 
characteristic of till sheets or terminal moraines, as well as the abun- 
dant swamps, lakes, and ungraded stream courses of such localities, are 
here practically absent. At numberless points within the area over- 
ridden by glacial ice the bedrock is scratched, grooved, and smoothed, 
while within the Driftless Area glacial markings are entirely absent.^ 
The thoroughly dissected upland plain of the Driftless Area is in strik- 
ing contrast to the more even country with drift-filled valleys about 
it. The valleys and ravines tributary to the main streams have been 
thoroughly organized and the divides reduced to narrow ridges. The 

1 Grant and Burchard, Lancaster-Mineral Point Folio U. S. Geol. Surv. No. 145, igo7, 
p. I. 



PRAIRIE PLAINS 



495 




Scale of Miles 

Fig. ig2. — Driftless Area of Wisconsin. 

valley bottoms toward the south are from 600 to 700 feet above sea 
level, and the relief of the area is from 200 to 300 feet.^ 

In spite of the extreme irregularity of the drainage of the glaciated 
region its relief is less than that of the Driftless Area, a condition due 
to the manner of distribution of the drift, which in general was lodged 
in the valleys more freely than on the heights. Such plain-like qualities 
as the drift-covered region exhibits are due less to the glacial denudation 

1 J. E. Carman, The Mississippi Valley between Savanna and Davenport, Bull. 111. State 
Geo!. Surv. No. 13, igog, p. 2g. 



496 



FOREST PHYSIOGRAPHY 



of prominences than to the grading up of depressions. In a rough 
manner the driftless region therefore presents the essential features of 
the preglacial topography of this portion of the United States.^ 

The purely residual products in the Driftless Area have their greatest 
expression upon the flat-topped upland areas. On the valley slopes 
the residual products tend to be removed by erosion, and on the valley 
bottoms there is alluvial filling derived from the uplands in part during 
an earlier period of alluviation (probably glacial) and in part by wash 
under existing conditions." 

The Driftless Area has created widespread interest since early in the 
eighteenth century, largely because it has not that exceptional height 
which on the border of the glaciated country is the general cause of 
immunity from continental glaciation. Its average summit level falls a 




Fig. 193. 



Diagrammatic section in the Driftless Area, showing relation of the mantle rock to the solid 
roclc beneath. (Alden, U. S. Geol. Surv.) 



little short of 1 200 feet, while the effective height of the highlands lying 
between it and Lake Superior is from 1700 to iSoo feet. The summit 
level between the Driftless Area and the plains of Iowa and southern 
Minnesota is about 1300 feet, so that as a whole the Driftless Area 
is somewhat lower than the surrounding tracts. Furthermore, the 
immunity from glaciation enjoyed by the area was due not to some 
accidental condition but to a geographically fixed cause, for none of 
the repeated invasions of the ice affected it.^ 

The most important elements of the explanation of the Driftless 
Area are that it is in the lee of the elevated territory of northern Wis- 
consin and Missouri, which acted as a wedge, forcing the ice away on 
either side and protecting the region south of it,^ and that the great 
valleys of Lake Superior and Lake Michigan lie in such position with 
reference to the Driftless Area as to tend to divert the glacial streams 

1 Chamberlin and Salisbury, The Driftless Area of the Upper Mississippi, 6th Ann. Rept. 
U. S. Geol. Surv., 1884-85, p. 307. 

2 S. Weidman, The Geology of North-Central Wisconsin, Bull. Wise. Geol. and Hist. 
Surv. No. 16, 1907, p. 554. 

' Chamberlin and Salisbury, The Driftless Area of the Upper Mississippi, 6th Ann. Rept. 
U. S. Geol. Surv., 1884-85, p. 315. 

* N. H. Winchell, 5th Ann. Rept. Geol. and Nat. Hist. Surv. of Minn., 1877, p. 36. 



PRAIRIE PLAINS 497 

to right and left and thus to increase the eifect of the highlands lying 
between the lakes in turning the ice from the driftless region.^ A 
third cause is found in the retarded feeble flow and relatively increased 
wastage caused by the thinning ice through the diversion of the main 
lobes down the lake troughs. An important factor was the broad 
zone of glacial wastage which probably includes approximately 150 miles 
of the ice border; on this assumption the meager ice streams that crept 
down across the highlands south of Lake Superior and the enfeebled 
tongues which crept down the adjacent depressions were profoundly 
controlled by the topography and easily directed this way and that 
according to the relations of the major topographic depressions. 

It is also maintained with much reason that the outlines of the ice 
front would be modified to an important degree by the law of self- 
perpetuation of climatic conditions; by which is meant that the ice-clad 
regions increased the snowfall upon themselves and tended toward self- 
perpetuation, just as the ice-free and therefore relatively warmer area 
resisted the advance of the ice by excessive melting. While this last 
agency was not an originating one it would undoubtedly produce a 
modifying effect and tend to cooperate with the topography in holding 
the surrounding ice to the depressions down which the invasion first 
took place. 

The Driftless Area is interesting ecologically because of the occur- 
rence therein of many plants peculiar to it alone. Among these mosses 
and other low forms predominate. 

' R. D. Irving, Geology of Wisconsin, vol. 2, 1877, pp. 608, 611, 632, 634. 



CHAPTER XXV 

ATLANTIC AND GULF COASTAL PLAIN (INCLUDING THE LOWER 
ALLUVIAL VALLEY OF THE MISSISSIPPI) 

General Features and Boundaries 

The greater part of the eastern and southern coasts of the United 
States is bordered by a lowland whose physiographic features are de- 
veloped upon a mass of soft sands, silts, and clays, chiefly of Cretaceous 
and Tertiary age, and disposed in strata that incline (dip) gently sea- 
ward. The structural features are in the main very simple, though in 
places there are important departures from the average condition. On 
the north shore of Long Island the clays (Cretaceous) were disturbed by 
ice action and quite generally concealed by a cover of glacial and fluvio- 
glacial material; in Louisiana important faults complicate the struc- 
ture, topography, and drainage; in Oklahoma and Texas some of the 
coastal plain deposits are indurated, not soft and friable as generally; 
and in many localities the dip of the strata, almost never great, varies 
from a mean sufficiently to cause important differences in the width of 
the coastal tract, the character of the shore line, and the general topo- 
graphic expression. 

The Coastal Plain terminates on the north at Cape Cod, on the south 
in Mexico. Both ends are narrow and the northern is glaciated and 
partly submerged. The physiographic features of the province are 
varied at two places by special features of the first order — the peninsula 
of Florida and the lower alluvial valley of the Mississippi. Its width 
varies from a fraction of a mile to 500 miles measured normal to the 
coast; its greatest inland development is in the Mississippi Valley, where 
it swings northward into western Kentucky, southeastern Missouri, and 
eastern and southern Arkansas. The inner edge of the northern portion 
of the Coastal Plain is bordered by water bodies — Cape Cod Bay, Long 
Island Sound, etc. ; by an inner valley lowland in New Jersey, Alabama, 
and Arkansas; and these features in turn are bordered by various topo- 
graphic provinces — the Piedmont Plateau developed on crystalline rocks 
at the north and east and in succession westward and southward, the 
Appalachian Mountains and Plateaus, the Ozark Highlands, the Oua- 
chita Mountains, and the Prairie Plains of central Texas. 

498 



ATLANTIC AND GULF COASTAL PLAIN 499 

Fall Line 

The Atlantic division of the Coastal Plain borders the Piedmont 
Plateau along the fall line, as it is commonly termed. This phrase im- 
perfectly describes the boundary, which is not really a line but a zone 
of appreciable width; hence "fall belt" would be a more accurate desig- 
nation. As the streams cross from the old land or Piedmont Plateau to 
the new land or Coastal Plain they descend over rapids and falls of 
moderate height. Between the Raritap and the Roanoke the rivers 
discharge directly from rock-walled channels into tidal estuaries, since 
here the depressed land has brought the sea to the very borders of the 
Piedmont Plateau; but farther south the fall line is above sea level; on 
the James it is at tide level; on the Neuse 100 feet above the sea; on 
the Wateree, near Camden, it is 125 feet; on the Savannah, near Au- 
gusta, 125 feet; on the Chatahoochee, near Columbus, 210 feet; and on 
the Tuscaloosa at Tuscaloosa, 150 feet. 

On the interfluves. Coastal Plain and Piedmont Plateau merge 
into each other in an intermediate zone from a fraction of a mile 
to 10 or 12 miles wide. The boundary is never a cliff and seldom even 
a well-defined scarp, and the lowland hills are nearly as rugged and 
more than half as high as the piedmont hills; but chiefly on account of 
differences of soil the two provinces present some of the most strongly 
marked contrasts in the United States, if not in the world. In the 
Piedmont Plateau the rocks are crystalline, the soils residual, the stream 
courses flow in narrow gorges with cataracts and rapids; while in the 
Coastal Plain the soils are derived from clay, sand, and gravel deposits, 
and the streams flow in shallow valleys and discharge into broad tidal 
estuaries or coastal swamps. In the piedmont region the topographic 
details, the soils, and the watercourses reflect the character of the rock, 
while in the coastal region these features represent the work of streams 
born upon plains newly uplifted from the sea, or reflect the general attitude 
of the lowland rather than its rock character. Among the important 
cities located upon the common boundary of these two great provinces 
may be mentioned Raleigh, Camden, Columbia, Augusta, Macon, Colum- 
bus, Montgomery, Tuscaloosa, Little Rock, Austin, San Antonio, etc. 

Relation to the Continental Shelf 

The seaward limit of the coastal lowlands on the southeastern border 
of the United States is a steep scarp which marks the transition from the 
outer edge of the shallow continental shelf to the abysmal depths of the 
main ocean floor. This scarp forms the true continental margin and is 



500 FOREST PHYSIOGRAPHY 

comparable in height and extent though not in topographic variety 
with some of the most majestic mountain ranges. Were sea level 
lowered to its foot, present sea level in this latitude would be a region 
of ice and snow. The seaward slope of the Coastal Plain is -continued 
as the continental shelf beneath the level of the sea to distances varying 
from loo to 200 or more miles; the Coastal Plain is therefore to be 
considered as the landward extension of a greater plain whose outer 
border is submerged. The present position of the shore line upon this 
plain is a purely accidental one and subject to change, indeed is now 
changing at what from even a human standpoint may be considered 
a rapid rate. The steady depression of the larger part of the coast is 
so pronounced that if continued the sea will in a very short time again 
cover the coastal lowlands. In more recent periods of the earth's his- 
tory such transgressions of the sea over the land have been frequent 
and important, and no less important have been the various retreats of 
the sea which have brought the coastal border of the continent out 
near the border of the continental shelf and turned what is now conti- 
nental shelf into dry land. 

The repeated invasions of the sea are clearly indicated by the marine fossils found in the 
flat-lying sediments which constitute the Coastal Plain; and the surface of the continental 
shelf is deeply scored opposite the mouths of many of the coastal rivers by trenches or sub- 
marine canyons whose position and character have led to the conclusion that they represent 
old river valleys formed at a time when the land stood higher than now. 



Materials or the Coastal Plain 

ATLANTIC SECTION 

The lowest strata of the Atlantic Coastal Plain, as illustrated in the 
Maryland section, are composed of arkosic sands and clays derived 
from a deep mantle of disintegrated gneiss and phyllite such as now 
form part of the Piedmont Plateau. The sands and clays have de- 
tached outliers west of the main border of the Coastal Plain which 
show by their position, altitude, and composition that the plains strata 
formerly extended farther west over the adjoining portion of the Pied- 
mont Plateau. Higher in the section the strata consist of variegated 
clays and coarse, irregularly bedded sands. Then follow sands and clays 
in alternation with but slight variations in character and a gradual 
transition toward sandy and marly deposits.^ 

1 C. Abbe, Jr., A General Report on the Physiography of Maryland, Including the Develop- 
ment of the Streams of the Piedmont Plateau, Md. Weather Serv., vol. i, pt. 2, pp. 74-75. 



ATLANTIC AND GULF COASTAL PLAIN 501 

GULF SECTION 

The Gulf Coastal Plain section is rather typically represented in the 
Arkansas-Louisiana district where the lowermost beds are sandy and 
contain vegetable remains and brackish- water shells. Above these basal 
beds are limestones and marls; higher in the section are sands, lignitic 
clays, marls, and chalks, a succession indicating a gradual deepening of 
the water in which the sediments accumulated. Succeeding the deep- 
water deposits are limestones, marls, and lignitic sands, showing a return 
to shallow-water conditions.^ Then came complete and final uplift of 
the region and the formation of a coastal plain out of what had long 
been a continental shelf. The migration of the shore zone, characterized 
by sand deposits, over the surface of the plain from its inner to its outer 
edge was the last important geologic event and is the cause, of the 
prevailingly sandy nature of the surface deposits. 

Subdivisions 

(i) Including a broken and glaciated northern section the Coastal Plain 
may be said to fall into seven well-defined districts. The first includes 
Cape Cod, Martha's Vineyard and Nantucket islands. Long Island, 
and a number of lesser islands. 

(2) The second extends from the Hudson to the Potomac, and is char- 
acterized by a cuesta, an inner lowland, and a gentle outward slope or 
lowland merging into great estuaries that nearly isolate it from the 
mainland. 

(3) The third extends from the Potomac to the Neuse. It is a low east- 
ward-sloping plain characterized by long arms of the sea reaching far 
into it, by broad terraced plains of loam, and broad coastal sounds 
defended on the seaward border by long tenuous reefs partly of sand, 
partly the narrow and wave- and current-modified outcrops of clayey 
formations (Cretaceous) that dip seaward.- 

(4) The fourth section extends from the Neuse to the Suwanee as a 
gently sloping plain characterized by great stretches of pine-covered sands 
with swampy marginal development also fringed by coastal reefs. 

(5) The fifth section extends from the Suwanee River to the bluffs at 
the eastern border of the Mississippi flood plain. This division has more 
important topographic irregularities than the Georgia-South Carolina 
section of the Coastal Plain, its inner border having been dissected in 

1 A. C. Veatch, Geology and Underground Water Resources of Northern Louisiana and 
Southern Arkansas, Prof. Paper U. S. Geol. Surv. No. 46, 1906, pp. 20-28. 

2 CoUier Cobb, Notes on the Geology of Currituck Banks, Jour. Mitchell Soc, vol. 22, No. i, 
p. 17. 



502 FOREST PHYSIOGRAPHY 

such manner as to develop a rather typical inner lowland and cuesta. 
Along the coast are long narrow keys, some of which are scarcely able to 
maintain themselves owing to the depression of the land and to the 
encroachment of the waves, while some are completely submerged and 
have the form of offshore shoals. The seaward border of the Coastal 
Plain of this section is marked by broad lagoons, low coastal swamps, 
and extensive savannas. 

(6) The sixth section is the low, poorly drained, swampy terminus of the 
flood plain of the Mississippi, an area whose southern end is scarcely yet 
reclaimed from the sea. 

(7) The seventh section extends from Atchafalaya Bayou to the Rio 
Grande. Its interior development is topographically weak except in 
Arkansas and Louisiana, where a somewhat regular series of cuestas and 
inner and outer lowlands has been developed. The seaward margin of 
this district is bordered by swamps, extensive sounds, and long narrow 
lagoons.^ 

Cape Cod-Long Island Section 

Cape Cod 

The northernmost section of the Coastal Plain is broken by dissection 
and drowning into a number of islands, shoals, and capes of which the 
most important members are Cape Cod and Long Island. Lesser 
members are Staten Island, Block Island, and Martha's Vineyard and 
Nantucket islands. 

That these are all members of a formerly more extensive and less dissected coastal plain 
fringe is inferred from (i) the evidences that stream courses on the present mainland border are 
superposed from a former cover of gently and regularly sloping marine deposits; (2) the actual 
finding of fragments of such deposits at Marshfield,^ Boston,^ and Third Cliff,^ at the first two 
locahties below sea level and at the third above it; (3) the occurrence of known Tertiary de- 
posits'- on Georges Bank east of Cape Cod in line with the general trend of the strike of the 
unsubmerged portions of the plain to-day; and (4) from the general likeness of the shoal and 
channel outlines of the sea floor north of Cape Cod to drowned valleys." 

1 For a characterization of these various districts and a clear description of the coastal plain 
of the southeastern portion of the United States, see W J McGee, The Lafayette Formation, 
12th Ann. Rept. U. S. Geol. Surv., 1890-91, pt. i, pp. 353-521, with four excellent maps, 
photographs, and cross sections. 

2 C. H. Hitchcock, Final Report on the Geology of Massachusetts, vol. i, 1841. 

» F. G. Clapp, Clay of Probable Cretaceous Age at Boston, Massachusetts, Am. Jour. Sci., 
vol. 23, 1907, pp. 183-186. 

* I. Bowman, Northward Extension of the Atlantic Preglacial Deposits, Am. Jour. Sci., 
vol. 22, 1906, pp. 313-325. 

5 A. E. Verrill, Occurrence of Fossiliferous Tertiary Rocks on the Grand Bank and 
Georges Bank, Am. Jour. Sci., 3d Series, vol. 16, 1878, pp. 323-332. 

6 N. S. Shaler, The Geology of the Cape Cod District, i8th Ann. Rept. U. S. Geol. Surv., 
pt. 2, 1896-97, pp. 516, 578, 580. 



ATLANTIC AND GULF COASTAL PLAIN 503 

Cape Cod is the most extreme projection on the eastern coast of the 
United States north of the peninsula of Florida. In general outHne it 
roughly resembles a great flexed arm, the southern portion being the 
humerus, the eastern portion the forearm, and the northernmost ex- 
tremity the clenched fist. It is so narrow at the base where it adjoins 
the mainland that a canal is building to connect Cape Cod Bay and 
Buzzards Bay; the land section will be only 8 miles long. Its exposed 
position, the lack of good harbors, and its featureless shores combine to 
give the Cape notoriety as one of the two graveyards of the Atlantic. 
The projection of the Cape eastward and northward would not seem 
so remarkable if the material composing it were solid rock of great 
resistance to wave erosion ; as a matter of fact no hard rock occurs upon 
it, only soft, easily washed gravel, sand, and clay. 

The extreme northern end of Cape Cod, the wrist and fist of the Cape 
Cod arm, is composed of wave- and current-derived material entirely. 
It is low, covered with sand dunes of irregular outline, bears a scanty 
growth of shrubs and grasses or is entirely bare of vegetation, and has 
well-rounded coastal outlines where the wear of currents and waves is 
constantly reshaping the beach. The material added to the Cape at 
this point is derived from the crumbling eastern side of the arm. The 
attack of the waves on the steep eastern shore is vigorous and sustained, 
and at the present rate of retreat, 3.2 feet per year, the Cape will be 
entirely destroyed 8000 to 10,000 years hence. On the western side 
of the Cape the shore is low and flat and bordered by wave-built sand 
reefs which enclose extensive lagoons. Cape Cod is relatively quiet, a 
great natural harbor, yet the shore currents are here attacking the 
border of the Cape and assisting in its demolition.^ The same action is 
exhibited at Monomoy Point, the southeastern extremity of the Cape, 
where a portion of the material torn from the bold eastern margin of 
the Cape is drifted southward and built into a long flying sand reef. 

The foundation of a large part of Cape Cod is a mass of preglacial sands and clays pre- 
sumably of Cretaceous or Tertiary age, revealed in well sections, clay pits, cuts, and bluffs. 
These deposits form the substructure of the east-west section of the Cape where they occur 
above sea level. The north-south section nowhere reveals similar deposits above sea level, 
but they have been encountered in well borings. The morainal ridge that forms so promi- 
nent a feature of the first-named section rests upon these preglacial deposits and its height is 
enhanced thereby .2 

The surface material of the Cape is, however, not derived from the 
basement deposits; it is of glacial derivation. It occurs in the form 

• W. M. Davis, The Outline of Cape Cod, Proc. Am. Acad. Arts and Sci., vol. 31, 1896, 
pp. 331-332. 

2 N. S. Shaler, The Geology of the Cape Cod District, i8th Ann. Rept. U. S. Geol. Surv., 
pt. 2, 1896-97, p. 534. 



S04 FOREST PHYSIOGRAPHY 

of a thin veneer of till except (i) where actual morainic ridges of excep- 
tional thickness occur, or (2) where outwash deposits were laid down in 
front of the moraine. Cape Cod is therefore a mass of glacially derived 
material resting upon a preglacial basement of sands and clays. Its 
detailed surface features are due chiefly, and in some cases wholly, to 
ice action. Lakes are relatively abundant; the surface is character- 
istically pitted with kettle holes; unsorted material, till, is common; and 
there are many erratic ice-rafted bowlders. The glacial material is 
prevailingly sandy and this also is the character of the outwash plains 
that front the moraine. Lying well forward of the main line of the 
coast where no topographic prominences afford shelter from the wind 
the Cape is exposed to the fury of every tempest and its porous, light, 
dry material has been largely blown into dunes and drifts of sand. This 
is especially true on the immediate shore, where dunes of' considerable 
height occur and where serious effort has been made to stop the progress 
of the wind-drifted material. 

CONTROL OF SAND DUNES 

The problem of dune control is a paramount one in the utilization of 
large portions of the surface of Cape Cod. Similar efforts are required 
in many other localities in the United States, and since these are more 
or less alike in natural features and involve the same problems, the fol- 
lowing general discussion is included here. 

The chief areas of shifting dunes to be found along the Atlantic coast 
are on Cape Cod, near Provincetown ; southern New Jersey, near 
Avalon and Stone Harbor; Cape Henlopen, near Lewes, Delaware; 
Cape Henry, Georgia; Currituck Banks, North Carolina; Isle of Palms, 
near Charleston, South Carolina; and Tybee Island, near Savannah, 
Georgia. Sand dunes are also found on the Pacific coast in Ventura, 
Monterey, and Mendocino counties, California, and along the coast of 
Oregon.^ 

In California drifting sand has played an important part in obstruct- 
ing the channels in certain harbors on the coast; for example it has 
been blown into the channels every year near Eureka from a narrow sand 
spit several miles long between Humboldt Bay and the ocean.^ Very 

1 A. S. Hitchcock, Controlling Sand Dunes in the United States and Europe, Nat. Geog. 
Mag., vol. IS, 1904, pp. 45-47- 

2 S. B. Kellogg, Problem of the Dunes, Cal. Jour. Tech., vol. 3, 1904, pp. 156-159. See 
this paper for a discussion of various kinds of schemes for controlling sand dunes by sand- 
binding grasses, such as beach grass {Ammophila arenaria) and "rancheria grass" [Elymus 
arenarius); and for a photograph of a dune covering a forest above Fort Bragg, Mendocino 
County, Cal. 



ATLANTIC AND GULF COASTAL PLAIN 505 

troublesome dunes are developed on a large scale along the Columbia 
River in Oregon and Washington from Dallas to Riparia, from sand 
blown about over the flood plain of the Columbia, which is widely ex- 
posed during the dry season. Dunes occur in large numbers also about 
the southern end of Lake Michigan, on the eastern side of Lake Michigan, 
and east of Lake Huron. 

The most important principle of control of sand dunes is the establish- 
ment of a cover of material that will prevent drifting, the type of cover 
usually depending upon climatic conditions, cost of material, etc. Where 
possible it is best to produce a forest cover, for this is permanent and, if 
properly managed, yields an income. For this purpose the land must be 
temporarily fixed in some other manner than by seedlings, and a tem- 
porary binding of inert material such as brush, sand sedges, etc., may 
suffice. Beach grass has given most satisfactory results in the Great 
Lake region, North Carolina, and Europe. The grass is transplanted 
in the spring or fall and set 2 or 3 feet apart in the sand. It has the 
power of continuing to grow up through a cover of drifted sand by 
establishing root systems at constantly higher levels. If the sand is 
temporarily fixed by these or other means, young trees, usually conifers, 
may be planted and a forest estabhshed. In southwestern France a 
forest has been established by sowing the seed of Pinus maritima upon 
the sand and covering with brush. In France and on the coast of Prussia 
it has been found necessary in places to construct long artificial barrier 
dunes between the ocean and the forest and to fix the barrier dunes 
by beach grass and maintain them by constant oversight. In northern 
Europe the trees employed for reclamation of sand dune tracts are 
Pinus montana, Pinus laricio, Pinus austriaca, and Pinus sylvestris.^ 
Extensive pitch-pine plantations are now being experimented with on the 
sandy areas of Cape Cod, Martha's Vineyard, and Nantucket.^ 

Nantucket and Martha's Vineyard 

The relief and drainage of Nantucket Island afford many parallels to 
the conditions on both Cape Cod and Long Island. There is a terminal 
moraine on the northern shore of the island and a very irregular pri- 
mary or inner shore; the same kind of outwash plain is built forward of 
the moraine, pitted with kettle holes and creased by shallow drainage 
ways dry for the greater part of the year; and long tenuous sand reefs 
and flying spits occur like those on the coasts of the adjacent islands. 
Underneath the thin mantle of glacial materials lie preglacial deposits 

1 S. B. Kellogg, Problem of the Dunes, Cal. Jour. Tech. vol. 3, 1904, p. 47. 

2 Yearbook Dept. Agri., 1909, p. 336. 



5o6 FOREST PHYSIOGRAPHY 

which in places project above the level of the sea, so that were the 
glacial accumulations removed a number of small islands would still 
exist where Nantucket stands. For the most part the older surface is 
masked by glacial till and outwash gravels. The original x)utline of 
the island has been much altered by wave and current action; portions 
of the shore have been cut away, while other portions have been 
fringed with recently formed marine deposits.^ 



OYSTER POND 



SEA LEVEL S.E. 



FaOWTAL MORAINE KAH£8 TERRACE DRIFT 

Fig. 194. — Diagrammatic section of Martha's Vineyard. (Shaler, U. S. Gaol. Surv.) 

Martha's Vineyard lies west of Nantucket and has closely allied 
physiographic features. Not only are the deposits of the island of the 
same general nature but they are also disposed in roughly the same 
way, so that the northeastern and northwestern sides of the triangular 
island are hilly and morainic, with irregular shores, while the southern 
side is an almost straight eastward- trending line. It presents almost 
wholly those features typical of a morainal island. The surface drift is 
almost everywhere thin (about 10 feet) and as on adjacent islands it to 
some extent masks the older basement material, Fig. 194. The straight 
southern side of the island is a sand reef enclosing a large number of 
water bodies with a branching pattern closely resembling that of a 
stream system and tributaries, a condition signifying a slight sub- 
mergence of the land after the formation of the outwash plain bordering 
the shore.^ 

Long Island 

general geography 

To a forester Long Island is of peculiar interest. It supports a con- 
siderable variety of forest trees under special conditions, and the rela- 
tions of these to the physical conditions are the more easily determinable 
because of the detailed studies made by the United States Geological 
Survey and the Soil Survey. The value of the natural resources of 
Long Island is unusually great because of their proximity to a great 
consuming center; and detailed studies of its climate, soil, water supply, 
and physiography have therefore been made. 

The greatest length of Long Island (the "Lange Eyelandt " of the early Dutch) is ii8 
miles and its greatest width 23 miles. Its outline suggests the shape of a huge fish; the flukes 

1 Curtis and Woodworth, Nantucket, a Morainal Island, Jour. Geol., vol. 7, 1899, pp. 226- 
236; N. S. Shaler, The Geology of Nantucket, Bull. U. S. Geol. Surv. No. 53, 1899. 

2 For geologic description see N. S. Shaler, Report on the Geology of Martha's Vineyard, 
7th Ann. Kept. U. S. Geol. Surv., 1885-86, pp. 303-363. 



ATLANTIC AND GULF COASTAL PLAIN 



507 



of the tail are represented by Orient and Montauk points on the east; the head is represented 
by the blunt western end with its mouth-Hke extension at Coney Island. The south shore 
is double: the inner or primary shore hne is the border of a broad lagoon — Great South Bay 
and its extensions; the outer shore line consists of narrow sand reefs of remarkably regular 
outline. The eastern half of the northern shore is without notable indentations, but the west- 
ern half is deeply embayed by a dozen or more well-developed fiords with steep sides and note- 
worthy depth of water. 

■ GLACIAL TOPOGRAPHY 

TERMINAL MORAINES 

The principal relief features of Long Island are associated with a 
double line of eastward-trending glacial moraines fronted by extensive 
outwash plains of loose alluvium, Fig. 195. The southernmost is known as 




LEGENDI 

Covered with ic6 at the Ronkonkoma $tago 
Covered with Ice at the Harbor Hill stags 



73" 



7V 



Fig. 195. 



Relative positions of the ice during the two stages of the Wisconsin glaciation. 
(Veatch, U. S. Geol. Surv.) 



the Ronkonkama moraine. Its eastern extension gives character to that 
end of Long Island, and with the eastern extension of the Harbor Hill, 
or northern, moraine encloses a large body of water known as Peconic 
Bay. The Ronkonkama moraine is remarkable for the large body of 
water it encloses and after which it was named. Lake Ronkonkama. 
This is by far the largest lake on Long Island and extends about 25 feet 
below sea level. The two moraines are often referred to as the back- 
bone of Long Island, though it should be noted that it is a compound 
backbone, for east of Huntington the two moraines diverge more and 
more and enclose broad sub-level tracts between them. 

The seaward slope of a large part of the eastern half of the northern moraine has been 
largely removed by wave and current erosion, and in a few localities this has been carried so 
far that in the wave-cut clififs are exposed sections of the outwash plain through the complete 
removal of the moraine once fronting and guarding it on the north. Everywhere along this 
shore the projecting headlands are being modified by vigorous wave action. Cliffs are kept 



5o8 FOREST PHYSIOGRAPHY 

perpetually freshened and so steep that landslides are a common occurrence, bars are being 
built across the bay mouths, and in the mill of the surf the bowlders and stones of the crum- 
bling moraine are fast being ground to pieces. 

The Montauk moraine Hes chiefly in the interior of the island and is not subjected to such 
general attack by shore processes though its eastern extension, exposed to all the fury of 
Atlantic storms, is being battered rapidly to pieces. That the extreme eastern end must once 
have extended farther east is self-evident. Erosion has now progressed so far that portions of the 
once more extensive outwash plain have been destroyed. 

Both moraines bear the usual marks of terminal accumulations formed 
by a continental ice sheet. Their surfaces are deeply pitted by large 
and small kettle holes, and enclosed, formless pits and depressions, and a 
maze of mounds, knobs, and ridges of till and other glacial debris still 
further diversifies their surfaces. Upon the floors of some of the en- 
closed depressions lakelets or swamps occur, and all others are dis- 

. ^ n^'i'ra terminaL'moraine ". "^ o °^ 




Fig. 196. — Section showing the relation of outwash to terminal moraine. (U. S. Gaol. Surv.) 

tinctly moist, but by far the larger number are without standing water. 
Large portions of both moraines are composed of till of rather typical 
composition, but there are also large portions which are composed 
largely and in some localities almost exclusively of sand. The sandy 
phases are developed chiefly at the eastern end, the clayey phases 
at the western end of the island. Bowlders, large and small, are 
scattered freely upon the surfaces and throughout the mass of both 
moraines. They are of variable composition; gneisses and schists, 
sandstones and quartzites predominate. 

OUTWASH PLAINS 

Long gently sloping outwash plains extend southward from both 
moraines. Their northern margins are in many places pitted by kettle 
holes, and a considerable number of old broad drainage grooves cross 
them from north to south. The grooves are not now effectively occu- 
pied by streams, for the present drainage consists chiefly of small wet- 
weather streams extremely diminutive as compared with the ancestral 
streams whose channels they occupy. The old broad channels have a 
markedly asymmetric development, the steepened slope being on the 
west, a response, it is thought, to the right-handed deflective influence 
of the earth's rotation in the northern hemisphere.^ 

The porous nature of the outwash material greatly reduces the run- 

1 G. K. Gilbert, The Sufficiency of Terrestrial Rotation for the Deflection of Streams, Am. 
Jour. Sci., 3d Series, vol. 27, 1884, pp. 427-432. 



ATLANTIC AND GULF COASTAL PLAIN 



509 



ofif, and instead of a normal run-off of about 40% the run-oflf is about 
60% of the total precipitation. The reduced run-off has retarded the 
dissection of the frontal plains, and the small elevation has favored the 




Fig. 197.- 



-Outwash plain in foreground, the hills in the background are preglacial and have but a slight 
morainal covering. (Veatch, U. S. Geo). Surv.) 



same result. They extend mile after mile as almost flat plains of allu- 
vium in striking contrast to the ruggedness and picturesqueness of the 
terminal moraines. 




Ct.-_ oc 



Horizontal 



5 4 3 2 1 



Vertical 
lomiles 100050.0 looo 2000 3000 feet 



Fig. 198. 



■ Cross section of Long Island, showing glacial deposits (dotted) and pre-Cretaceous peneplain 
(Cr.). (Veatch, U. S. Geol. Surv.) 



TOPOGRAPHIC FEATURES RELATED TO STRUCTURE 

The present topography of Long Island can not be fully understood 
without some knowledge of the substructure, Fig. 198. Cretaceous and 
Tertiary sands of great thickness occur up to heights of several hundred 



5IO FOREST PHYSIOGRAPHY 

feet above sea level; their outcrops are exposed principally along the 
north shore, where the long, deep, and narrow fiords or reentrants re- 
veal good sections of the white and red sands and white clays of the 
Cretaceous formations. In the Half Hollow and Mannettb hills and 
distinctly beyond the limit of the ancient ice sheet preglacial sections 
also are exposed, and the strata (Tertiary) consist of fine fluffy sands 
without glacial material of any sort. From such exposures of pre- 
glacial material above sea level it follows that an island would now 
exist even if the glacial material were removed; and in fact such an 
island did exist before the glacial period, but it was an island of far 
gentler topography and much more regular outline. 

Upon a base-leveled and down- warped rock floor Cretaceous and Tertiary materials were laid 
down and afterward eroded as the result of uplift of the sea floor. The erosion was at first normal 
and resulted in the formation of an inner lowland where now Long Island Sound occurs. Fol- 
lowing this there were a number of emergences and submergences of complex character, during 
which the drainage of the inner lowland was first developed to the west and later, through the 
tilting of the land, to the east. 

The essential features of the present topography were developed after the Lafayette sub- 
mergence. The erosion of the inner lowland was continued to the point where a well-developed 
cuesta was formed, and it is to the further accumulation of glacial material upon the summit 
of this cuesta that Long Island owes its present marked contrast between rugged moraine and 
abrupt high northern shores on the one hand and smooth southern plain with low, reedy, fiat 
southern shores on the other. The scouring action of the ice sheet further deepened the inner 
lowland, and with the final disappearance of the ice from the region a sHght sinking of the land 
brought out even more strongly the features owing to depression. At a higher elevation the 
inner lowland of Long Island would have similar relations to the cuesta and the old-land as the 
inner lowland of New Jersey now has to the cuesta of the New Jersey coastal plain on the east 
and the old-land on the west. 

SOILS AND VEGETATION 

SOIL TYPES 

A soil map of Long Island, Fig. 199, shows four broadly defined 
types of soils: (i) stony loams and gravels which occupy the terminal 
m_oraines and the narrow plateau between the northernmost moraine 
and the north shore, (2) coarse sandy loams that constitute the greater 
part of the outwash plain, (3) fine sandy loams which form the outer 
fringe of the outwash plain and those portions of it that are adjacent to 
the old drainage ways, and (4) clay loams that form a transition type 
between the upland and the salt marsh and the beach sands. While 
the clay loams have greater natural fertility than the sandy loams they 
are often found on lands too rough for cultivation, and the great market 
gardens of the island are found on the outwash principally, where many 
of the conditions of cultivation are ideal. Agriculture has become so 
highly specialized in the western part of the island on account of prox- 
imity to New York City that the natural fertility of the soil is a far 
smaller factor than position with reference to the market. 



ATLANTIC AND GULF COASTAL PLAIN 



511 




TERMINAL MORAINES IN BLACK 




g^ STONV LOAMS AND GRAVEL 

GRAVEL AND COARSE SANDY LOAMS 
SAND (NORFOLK) 

CLAY LOAMS, FINE SANDY LOAMS, 
BEACH SAND, SALT MARSH 




FOREST TYPES 
IIRIE, SCRUB OAK, STUNTED OAK 



Fig. 199. — Terminal moraines, soils, and vegetation of Long Island. 




Fig. 200. — Characteristic growth of pitch pine (background) and scrub oak (foreground) on the outwash 

plains of eastern Long Island. 




Fig. 201. 
S12 



- The effects of repeated fires on soil and vegetation, Long Island. The raw soil with the 
humus almost entirelj' burnt out has the appearance of snow in the photograph. 




Fig. 202. — Typical growth of hardwood on the clayey portions of the Harbor Hill ninr.iine, Long Island. 




Fig. 203. — Scattered growth of pitch pine and scrub oak on the sandy portion of the Ronkonkama 
moraine south of Riverhead, Long Island. 

513 



514 FOREST PHYSIOGRAPHY 



NATURAL VEGETATION 



In the disposition of the natural vegetation we have a far truer index 
of soil fertility and water-supply conditions than in the artificial dis- 
position of farms. On the poor, dry, sandy, porous soil of t-he outwash 
plains the characteristic growth is pitch pine and scrub oak {Quercus 
nana and Quercus prinoides), as shown on the accompanying map, Fig. 
200. The natural prairie for which Long Island is famous is also located 
on the southern outwash plain in the vicinity of Hempstead and Garden 
City. It bears a growth of prairie grass and has never been covered 
with forests. In Dutch colonial days it was a famous pasture ground 
for sheep, horses, and cattle. On the better soils of the outwash plains 
a better growth of pitch pine is found, and even a small stand of white 
pine has been reported southeast of Sag Harbor. Where a slight 
admixture of clay or loam appears, as in a number of scattered 
lo(!alities, a few species of hardwoods grow with pine and oak. 

Upon the moister and more clayey moraines excellent growths of hard- 
woods occur, Fig. 202. Chestnut, oak, elm, beech, and locust constitute 
the principal types. In a few localities, as several miles southwest of 
Port Jefferson, the moraine and accompanying outwash are occupied 
by oak, but it is a stunted growth and reflects the infertile character of 
the Norfolk sand on which it grows, the distribution of the stunted 
species corresponding almost precisely with that of the Norfolk sand. 
The sandy phase of the Ronkonkama moraine south of Riverhead is 
occupied by pitch pine, which occurs up to the summit of the moraine, 
Fig. 203. A similar exception on the outwash is the occurrence of 
hardwoods along the southern shore, where the nearness of the water 
table to the surface has resulted in hardwood growths and the exclusion 
of pitch pine and scrub oak. 

New Jersey-Maryland Section - ; 

The coasts of New Jersey, Delaware, and Maryland are great penin- 
sulas formed by the drowning of the major valleys, and here the lesser 
waterways discharge through reedy swamps or shoal inlets into land- 
locked bays. In Delaware and Chesapeake Bays these secondary re- 
entrants are fronted by small banks and bars similar to those that 
fringe the outer shore except where low cliffs have been formed at the 
ends of finger-like extensions of land between bays. Formerly the whole 
section of the coast between Cape Hatteras and New Jersey stood at a 
higher level and was faintly sculptured by the draining streams, but 
later depression has submerged the lower ends of the valleys, where 



ATLANTIC AND GULF COASTAL PLAIN 



515 



4'!^ 



bays now exist, and the bays still preserve the characteristic dendritic 
plan of the Coastal-Plain drainage. While the submergence affects a 
large extent of the Coastal Plain the actual amount of depression has 
been astonishingly slight. The waters of Chesapeake Bay are so shallow 
that it is sometimes more miles to the shore from a given point in the 
bay than it is feet to the bottom of the bay. The depth of the water is 
seldom more than 18 feet and averages only 10 feet. Twenty-five feet 
of elevation would cause it to become a low coastal terrace.^ 

NORTHERN PORTION 

In the northern portion (New Jersey) of this section of the Coastal 
Plain there are extensive flats both along the coast and in the interior, 
but these range in elevation from about 40 feet on the coast to 130 and 
150 feet farther inland, and 200 feet in the highest part of the Coastal 
Plain. The tidal marsh 
of New Jersey lies prin- 
cipally between the 
beach of the Atlantic 
coast and the mainland ; 
but there is also a tidal 
marsh bordering Dela- 
ware Bay which is not 
fronted by a beach. 
The width of the marsh 
varies greatly from 
place to place and is 
from less than a mile 
in its narrowest portion 
to 5 or 6 miles between 
Great Bay and Atlantic 
City. It has its greatest 
development at the 
mouths of the larger 
streams, and along 
Delaware Bay attains a width of 5 miles. The sand reefs owe their 
height chiefly to dunes. During times of storm the sandy barrier reefs 
are piled up above normal water level and on becoming dry are blown 
into hills and ridges by the wind. As in the Maryland section, the 
shallow lagoon between the beach and the mainland is gradually being 
filled up with wind-blown material, vegetation, and sediments. The 
most striking feature of the Coastal Plain of New Jersey is the line of 

1 W J McGee, The Geology of the Head of Chesapeake Bay, 7th Ana. Rapt. U. S. Geol. 
Siirv., 1885-1886, p. 552. 




Fig. 204. — Sand reef, salt marsh, and coastal plain upland, 
coast of New Jersey. 



5i6 FOREST PHYSIOGRAPHY 

elevations extending in a northeast-southwest direction from the Navesink 
highlands on the northeast to Mount Holly on the southwest, elevations 
which include heights that approach 400 feet.^ These are due, curiously 
enough, to widely contrasted conditions, (i) The clays, sands, jnarls, etc., 
do not have great inequalities in hardness, but locally the material is 
cemented into more or less solid rock. This occurrence is most common 
at the junction of beds of different texture, and in some cases has reached 
the point where the rock is quarried. Many of the most prominent eleva- 
tions are capped by such cemented beds of gravel, sand, or marl, and owe 
their prominence to a protecting cap. (2) Many other prominences in the 
highest belt of the district by contrast owe their height to the extremely 
loose and porous condition of the material. The rainfall sinks into the 
material as into a sponge and does not run over the surface and erode it; 
consequently the hills formed on the outcrop of the most porous beds are 
at elevations comparable to the hills formed upon the hardest material. 
Few elevations of note in the highest part of the New Jersey Coastal 
Plain are without such a protecting cap of rock or loose gravel.^ 

The strata on the inner edge of this part of the Coastal Plain have 
been stripped from the crystalline rocks beneath in such manner that a 
valley lowland has been developed parallel to the highlands that cross 
the state diagonally. The lowland extends from Raritan Bay to Trenton, 
and marks the outcrop of a series of less resistant formations whose 
removal goes forward more rapidly than that of the crystallines and 
hard sedimentaries on the west or the higher coastal plain formations 
on the east. 

SOUTHERN PORTION 

The outer edge of the coastal plain of Maryland is bordered by long 
narrow sand reefs caused by shore drift and wave action. Behind them 
are shallow lagoons of variable width ranging from a fraction of a mile to 
4 or 5 iniles in Maryland. The eastern portion of the lagoon is formed 
by shallow marshes along the western edge of the sand reef; the western 
shore is formed by the low, half-submerged topography of the main- 
land, somewhat modified by salt marshes. The floors of the lagoons 
are very shallow and flat and are composed (a) of sand blown over from 
the beach dunes, (b) of mud deposited by the rivers and tides, and (c) of 
matted roots of marine vegetation.'^ 

The surface of the coastal plain of eastern Maryland is broad and 

1 R. D. Salisbury, The Physical Geography of New Jersey, Final Rept. of the Geol. Surv. 
of New Jersey, vol. 4, 1895, p. 54. 

2 Idem, p. 64. 

•■' C. Abbe, Jr., A General Report on the Physiography of Maryland, Including the Develop- 
ment of the Piedmont Plateau, Md. Weather Service, vol. i, pt. 2, p. 82. 



ATLANTIC AND GULF COASTAL PLAIN 



517 



even and resembles a smooth or gently undulating sea floor. Many por- 
tions are characterized by long interstream stretches of plane surface 
of considerable breadth.^ The inequalities of the outer border of the 
Maryland plain were produced during a submergence which took place 
in very recent geologic time (Pleistocene) ; the plain has been so re- 
cently raised above the sea and to so small a height that time enough 
has not elapsed for the streams of gentle gradients to drain the swamps 
and lakes located upon them. It is characteristic of the swamps that 




Contour intervals 10 feet 



Fig. 205. — Swampy divides in eastern Maryland between the Chesapeake and the Atlantic. The coastal 
plain is here so young and so little dissected that many of the original irregularities have not yet been 
destroyed. (Hurlock quadrangle, U. S. Geol. Surv.) 

they are disposed chiefly along the main divides, as though dissection had 
not yet progressed to the headward sections of the streams, Fig. 205. 
The surface has a gentle seaward slope upon which has been developed 
a characteristic drainage system; the pattern is irregularly branching or 
dendritic, with the small streams commonly making almost a right angle 
with the general trend of the larger streams at the junction. Small 
lakes and swamps dot the surface and are due to inequalities on the sea 
floor produced by wave and current action. 

Except in their expanded lower courses the streams are small and 
unnavigable and are characterized by broad, shallow valleys with very 
gentle side slopes and smooth contours. In the interstream areas of the 
southern counties of Maryland one may travel for miles and never cross 
a well-marked valley. Where forests grow they have still further re- 

' C. Abbe, Jr., A General Report on the Physiography of Maryland, Including the Develop- 
ment of the Piedmont Plateau, Md. Weather Service, vol. i, pt. 2, p. 84. 



5i8 



FOREST PHYSIOGRAPHY 



tarded the run-off, so that wet swamps occur in the original inequalities 
of the surface. Signs of stream sculpture are rare; the surface seems to 
preserve the outlines originally imposed by waves and currents. In con- 
trast to these streams are the tidal estuaries and the slow meandering 
creeks that cross the salt marshes and have low though steep banks 
deeply fringed with reeds. 

Virginia-North Carolina Section 

The physiography of the third district of the Coastal Plain is charac- 
terized by a gentle seaward slope, smooth and monotonous, interrupted 
by long tidal inlets. The rivers expand towards- their mouths in reedy 




Ssas&a^^jr'saas^ 



Fig. 206. — Cypress trees of the Dismal Swamp. (Norfolk Folio, U. S. Geol. Surv.) 

marshes or in broad shallow estuaries barred from the open ocean by 
wave-built reefs that stretch almost continuously from Cape Lookout 
to Cape Henry. The uplands and lowlands of this district have so 
little difference in altitude that they could be scarcely distinguished 
from each other if the lowlands were not almost at tide level. The 
lowlands are the bay bottoms or the tidal marshes or the broad savan- 
nas which the highest tides barely fail to reach; the uplands rise in 
irregular scarps from a few feet to 15 feet in height to form stretches. 



ATLANTIC AND GULF COASTAL PLAIN 



519 



of excessively flat plain. Farther from the coast there is again a zone 
of undulating surface; the depressions containing the waterways be- 
tween undulations are less conspicuous than in New Jersey and lower 
Maryland. Toward the fall line the surface is characterized by broad 
terraced plains with irregular margins, and smooth monotonous inte- 
riors whose borders are diversified by labyrinthine ravines. 







is 







Fig. 207. —Albemarle and Pamlico Sounds and bor- 
dering sand reefs, east coast of North Carolina. 



Fig. loit. — Chesapeake Bay and Delaware Bay and 
the principal bays tributary to them. 



South Carolina- Georgia Section 

That portion of the Coastal Plain between the Neuse River of North 
Carolina and the Suwanee of southern Georgia and Florida is a land of 
gentle slopes which incline from the fall line to the coast. It is a pine- 
clad, sandy plain with dendritic drainage. The seaward margin of 
this section is a wave- and current-built sand reef at the north and a 
line of sea islands at the south, that merge at the extreme south into 
long low islands locally known as "keys." 

Along the Altamaha River the overflowed river bottoms have been re- 
claimed to some extent by diking and ditching and are cultivated. Their 
position is excellent for rice culture, since irrigation water is easily 
applied. Agricultural operations have been confined principally to the 
diked river lands since the early part of the nineteenth century, and rela- 
tively small areas have been cropped on the uplands since the early 



520 FOREST PHYSIOGRAPHY 

abandonment of indigo growing and the decline and cessation of cotton 
production.^ Near Savannah these diked rice fields have been badly 
neglected in recent years, but the fertility of the tide-marsh soils is 
beyond question, and were drainage reestablished they would consti- 
tute a valuable addition to the farming lands of the coast. ^ 

In portions of eastern North Carolina the seaward margin of the 
Coastal Plain bears drainage ways which are merely natural depressions 
marked by a quick growth of water-loving shrubbery and in some areas 
no well-developed drainage courses occur. These are the savannas, or 
open fiat lands with badly drained soils that support a poor growth of 
pine and an undergrowth of berry bushes and bay and pitcher plants.^ 
Inland from the low coastal zone is the broad belt of pine-clad sands 
which more than anything else characterizes the section. It is a vast 
plain with sUght undulations, the depressions slightly accented by streams 
occurring in the form of old terraced scarps much dissected owing chiefly 
to the friable character of the material, and now having rounded bottoms 
and softly contoured sides. With increasing distance from the sea the 
land stands higher and higher, the streams are more active, the val- 
leys deeper, and the surface more undulating, often rising into rounded 
hills. Again, as in the north, the hills may be isolated and flanked by 
terraces or may constitute parts of broad interstream areas, and some- 
times the terraces extend a short distance into the Piedmont Plateau. 
The common boundary of plateau and plain is ill-defined as to topog- 
raphy but rather sharply marked as to drainage and soil characters. 

Alabama-Mississippi Section 

The great section of the Coastal Plain between the Suwanee and the 
Mississippi is topographically diversified by two pronounced scarps; the 
first one is the steep river bluffs along the eastern border of the Mis- 
sissippi flood plain, bluffs due to stream planation; the second is the 
cuesta of the Alabama-Mississippi section of the plain. The cuesta 
begins on the river bluffs overlooking the Mississippi in extreme western 
Kentucky, crosses the Tennessee-Mississippi boundary 50 miles east of 
the river bluffs, curves southeastward to within 50 miles of the head of 
Mobile Bay and dies out eastward. This feature represents the inward- 
facing slope of the dissected Coastal Plain of Alabama and Mississippi. It 

1 Milton Whitney, Soils in the Vicinity of Brunswick, Georgia, Cir. U. S. Bur. Soils No. 20, 
P- 3- 

= Milton Whitney, Soils in the Vicinity of Savannah, Georgia, Cir. U. S. Bur. Soils No. 
ig, p. 2. 

3 Milton Whitney, Soils of Pender County, North Carolina, Cir. U. S. Bur. Soils No. 20, 
pp. 1-2. 



ATLANTIC AND GULF COASTAL PLAIN 52 1 

stands 600 or 700 feet above sea level. The outer lowland averages 200 
feet lower, while the inner lowland is a broad trough often 100 and some- 
times 200 feet lower than the border of the cuesta. The inner lowland 
is from 20 to 25 miles on the average and extends eastward a short 
distance beyond Montgomery. The densest population of the state of 
Alabama outside the cities is found in the inner lowland where the Selma 
chalk has weathered into a tract known as the "black belt" because of 
its prevailingly black soils. These are highly calcareous residual clays 
and have a black color where they contain much organic matter. They 
are among the most fertile lands in the South. 

In the eastern counties of Alabama a limestone (Gladden) of the 
coastal-plain series, 200 feet or more thick, is extensively developed into 
caves and lime sinks with which are associated big springs. This for- 
mation is marked by the occurrence of strong limy black soils similar 
to the black prairie soils of the Selma chalk, but the topography is so 
broken and deeply eroded as to be in sharp contrast to the smooth-floored 
Selma lowland. 

After the Tertiary period a blanket formation was deposited upon the 
Coastal Plain. This is known as the Lafayette formation and is a man- 
tle of reddish and light-colored loams and sands with frequent beds of 
water- worn pebbles in the lower parts. It is from 25 to 30 feet thick on 
the average and formerly covered the entire Coastal Plain, resting un- 
conformably on the older formations. In general it is sympathetic to 
the topography, though in many large areas it has been in great part 
removed by erosion. Because of its widespread development it consti- 
tutes about four-fifths of the cultivated soil of the entire Coastal Plain 
of Alabama, and is the chief factor in affecting the character of the 
soils. ^ 

The Cretaceous and Tertiary beds of the Coastal Plain of Alabama 
have an average dip toward the Mississippi and the Gulf of Mexico of 
30 to 40 feet a mile. The surface of the Coastal Plain descends in the 
same direction at a much less rapid rate, about a foot per mile, so that 
in going toward the south from the Appalachian Plateaus one passes in 
succession over the beveled edges of these deposits from the oldest to 
the newest. Each formation with few exceptions occupies the surface 
in a belt proportional in width to its thickness and running nearly east 
and west. 

The sandy formations of the outer lowland are commonly character- 
ized by short steep slopes and frequent ravines, the shales by long 

1 E. A. Smith, The Underground Water Resources of Alabama, Geol. Surv. of Alabama, 
190?, p. 12. 



522 FOREST PHYSIOGRAPHY 

slopes and few ravines, and the calcareous formations by smooth-con- 
toured ill-drained valleys known as "black prairies." 

The inland margin of this district is even less definite than the neighboring regioii to the 
east. In western Georgia and eastern Alabama the rivers cascade over hard rocks to fonn 
sluggish stretches in the lowlands, but commonly an arm of sedimentary material extends miles 
into the adjacent plateau in an ancient estuary and the river transition is seldom sharp. In 
central Alabama, where the Coastal Plain overlaps the southern end of the Appalachians, long 
fingers of lowlands stretch into the valleys between the ridges. In northwestern Alabama the 
line of demarcation between the Cumberland Plateau and the Coastal Plain is so poorly defined 
that it can not be drawn except as a zone from lo to 20 miles wide. Still farther north the 
boundary between the Coastal Plain and the older formations coincides approximately with 
the course of the Tennessee River, though here and there occur outcrops of the older harder 
rock west of the river and outcrops of softer coastal-plain deposits east of the river. 

The trunk streams of the Alabama section of the Coastal Plain flow 
across the Cretaceous and Tertiary strata, while the tributaries flow in 
general parallel to the strike of the outcrops. The infacing or north- 
ward-facing slopes of the hills are precipitous, while the southward- 
facing slopes are gentle. The tributary streams generally flow at the 
base of the steep infacing slopes. The major streams of the region thus 
run transversely to the cuesta and preserve their ancient consequent 
courses gained after the last emergence of the coastal lowlands from 
the sea. The tributary valleys on the other hand respond to a large 
degree to the detailed geologic structure and have excavated abnor- 
mally large subsequent valleys along belts of weaker strata. They thus 
join the master streams almost at right angles, and their direction of 
flow conforms to a notable degree to the outcrop of the strata upon 
which they have been developed. 

The outer edge of the Coastal Plain of Alabama and Mississippi is 
rather sharply defined by a line of more or less dissected bluffs and 
hence appears as an upland when viewed from the south. The un- 
dissected interfluves are flat everywhere except for shallow depressions 
(of uncertain origin) sometimes containing ponds and bordered by a 
shrubby growth of gums. The border depressions are without stand- 
ing water and are usually grassy savannas or pine meadows without 
undergrowth.^ 

The southern border of this section of the Coastal Plain is in part 
not a coastal plain but a flood plain under the dominance of the Mis- 
sissippi River. It is commonly skirted by keys separated from the 
mainland by narrow sounds, but the keys are narrow and low and the 
sounds commonly broad, shallow, and irregular in outline, and pass here 

1 E. A. Smith, The Underground Water Resources of Alabama, Gaol. Surv. of Alabama, 
1907, pp. 250-251. 



ATLANTIC AND GULF COASTAL PLAIN 523 

and there into grass-grown marshes, landlocked bays, and tidal flats. 
The sand reefs commonly lie 10, 15, or 20 miles off shore. The bays 
and marshes are partly bounded on the Gulf side by low sand banks, 
while between the bays friable sands and loams stand in vertical cHffs 
5, 10, or 15 feet high. Instead of the high grounds and the low grounds 
of the Carolinas the entire surface of this portion of the alluvial valley 
of the Mississippi is low ground. The savannas are the most prominent 
features — broad tracts bounded by low scarps sloping steeply down 
and overlooking swamps, bays, and sounds. About the margins of the 
savannas are a certain amount of shrubbery and forests of pine or mag- 
nolia, but their interiors are often broad and imperfectly drained tracts 
of flat grass-land. The swamps are covered with reeds, sedges, and 
coarse swamp grass on their coastal sides, with live-oak groves on the 
coast rivers, and with canes and tangled shrubbery toward the interior.^ 

The border of the higher portion of the plain on the inner margin of 
the coastal swamps is often a confused belt of knobs, crests, divides, 
spurs, peaks, and buttresses smoothly rounded, divided by flat-bot- 
tomed valleys with innumerable ramifications. On the floors of the 
valleys streams wander through broad plains of sandy alluvium. The 
summits of the hills and knobs reach elevations of 200 feet above tide 
and the valley flats to half that height. The upper plain represents the 
older surface, the lower the younger, and it is evident that after the 
excavation of the valleys and gorges depression ensued and the ravines 
were clogged with debris washed down from the hills, the final episode 
being an uplift of the land sufficient to drain but not deeply to erode 
the savannas or grass lands of the valley flats. 

The 600-mile western border of this district is a line of bluffs of com- 
plex character which marks the border of a broad terrace, the bluffs 
consisting of a series of truncated spurs separated by ravines and 
broader valleys. At Memphis the bluffs are rounded and about 100 
feet in height. At Yazoo and at Vicksburg they are 200 feet above the 
Mississippi flood plain. The slope of the Coastal Plain of Tennessee is 
eastward from the Mississippi bluffs, so that the highest portion of the 
Coastal Plain is immediately on the bluff, a physical feature which in 
the early settlement of the region determined the position of the roads, 
for it was the highest and driest portion of the country. The outer bor- 
der of the district, the edge of the Mississippi flood plain, undulates very 
gently in long low sweeps sculptured into a labyrinth of rounded hills 

1 For a description of the shell hammocks and the coastal marshes, the character of their 
soil, etc., along the coast of Mississippi and Alabama, see E. W. Hilgard, Agriculture and 
Geology of Mississippi, i860, p. 373 ff. 



524 FOREST PHYSIOGRAPHY 

and long low valleys with a local relief not exceeding 200 feet and some- 
times as low as 50 feet. 

One of the most important physiographic conditions of this section 
of the Coastal Plain is related to the abandoning of the old fields and the 
removal of the forest cover. It appears that in a state of nature the 
drainage was accomplished without unduly rapid dissection of the fertile 
surface soil — a yellow loam from 3 to 7 feet thick. But when the 
oak forests were removed in the settlement of the country and the 
plantations abandoned during the Civil War, the hills, no longer pro- 
tected by a forest foliage, and the soil, no longer bound by the forest 
roots, were vigorously attacked by the streams- and gullied and chan- 
neled in all directions. Year by year the formerly fertile fields were 
invaded by gullies of ever-increasing width, the soil of long geologic 
growth disappeared down the stream-ways, and the land was gashed and 
harmed beyond belief. 

"The washing away of the surface soil . . . diminished the production of the higher lands, 
which were then commonly ' turned out ' and left without cultivation or care of any kind. 
The crusted surface shed the rain water into the old furrows, and the latter were quickly deep- 
ened and widened into gullies — 'red washes.' . . ." 

"As the evil progressed, large areas of uplands were denuded completely of their loam or 
culture stratum, leaving nothing but bare, arid sand, wholly useless for cultivation; while the 
valleys were little better, the native vegetation having been destroyed and only hardy weeds 
finding nourishment on the sandy surface. 

" In this manner whole sections, and in some portions of the state [Mississippi] whole town- 
ships of the best class of uplands have been transformed into sandy wastes, hardly reclaimable 
by any ordinary means, and wholly changing the industrial conditions of entire counties, 
whose county seats even in some instances had to be changed, the old town and site having, 
by the same destructive agencies, literally 'gone down hill.' " i 

Specific names have been given to the erosional features of this district: a "break" is the 
head of a small retrogressive ravine; a "gulf" is a large break with precipitous walls of great 
depth and breadth, commonly being one hundred or one hundred and fifty feet deep; a "gut" 
is merely a road-cut deepened by storm wash and the effects of passing travel. 

Mississippi Valley Section 

The sixth division of the coastal lowland is the great flood plain, or 
delta and flood plain combined, of the lower Mississippi. It is bounded 
on the east by a continuous line of bluffs and On the west by a conspic- 
uous ridge known as Crowley's Ridge (north) and by an alternating line 
of irregular bluffs and valleys (south). This alluvial district is one of 
the most extensive of the really low areas of the continent, l3dng prac- 
tically at base level. In the southern part of the district the surface 
approximates tide level and indeed the outer border consists of perma- 
nent tidal marshes. The surface is very ill-drained, and bayous, lakes, 
and abandoned channels constitute an irregular maze of water upon a 

1 E. W. Hilgard, Soils, 1906, pp. 218-219. 



ATLANTIC AND GULF COASTAL PLAIN 



525 



plain with scarcely perceptible slope. Between the waterways are ridges 
of slightly higher land, some of which are the natural levees of channels 
long since abandoned. In the western part of the district the inter- 
stream areas lie so high that they are invaded only by the highest floods, 
but the surface material is fine and compact and the surface itself ill- 
drained; consequently the trees are either drowned by the floods or with- 
ered by the sun in the droughts and the surface is without a forest 
cover. It supports a patchy growth of coarse grass, the patches being 
known as the "black prairies" of southern Arkansas and Louisiana. 

In the northern portion of the lower alluvial valley of the Mississippi 
extensive land tracts were converted into lakes, flowing rivers trans- 
formed into stagnant bayous with uplifted areas between, and some 




■29-05' 



-29^5 



89' 15 



Fig. 209. — Finger-like extensions of tlie Mississippi delta. The entire area shown as land is swamp-land. 



stream courses actually diverted during the series of earthquakes between 
1811-1813. This region includes the "sunk country" of Missouri and 
Arkansas and the "Reelfoot Lake district" of Kentucky and Tennessee, 
and forms the uplifted land of Lake County, Tennessee, one of the few 
sections of the Mississippi flood plain that escape the inundations of 
the highest floods. 

Between Lake Borgne and Mobile Bay the Gulf is advancing upon 
the land so rapidly that the coastal rivers are nearly submerged and 
occur as narrow mud banks like the Chandeleur Islands, or as com- 



526 . FOREST PHYSIOGRAPHY 

pletely submerged bars and shoals that parallel the coast. A further 
effect of submergence is shown in the excessive breadth of the lagoons. 

On either side of the immediate delta of the Mississippi the alluvium 
deposited by the great river has been modified by waves aiKi currents 
into bars and reefs and the shore has a smoothly trimmed effect in 
contrast to the finger-like extensions of the actively growing portion of 
the delta. In the latter case the rate of deposition exceeds the rate of 
current wear and the land is being built seaward.^ 

Meander development and sidewise bodily movement of the river as 
a whole have opened up a river lowland so flat as to make the coastal 
plains appear as uplands when viewed from the river. This lowland, 
the lower alluvial valley of the Mississippi, is from 30 to 60 miles wide 
and about 600 miles long. Over its flat surface the great Mississippi 
meanders in an extremely indirect course. Receiving the contributions 
of a vast network of tributaries themselves major streams, it is little 
wonder that the river is subject to numerous floods transmitted from 
the tributaries. Formerly they inundated a vast expanse of lowlands 
and were of yearly occurrence; now a system of restraining dikes or 
levees and expensive revetments partially restrain the great river, and 
floods are in a measure under control. At present the levee system com- 
prises about 1500 miles of structure and is about 71% completed. The 
number of square miles of overflowed land in 1903 was half the mileage 
for 1897. In 1882 there were 284 crevasses recorded; in 1903 there were 
only 9 of importance.^ 

The extent of alluvial bottom land that escapes inundation is ex- 
tremely limited. The higher tracts are confined chiefly to the river 
border, hence this is where the principal plantations are located. From 
the low natural levees the land slopes gradually away on either side 
to swampy back country covered with heavy forests of cypress and 
gum. The first problem in the utilization of these back swamps is 
drainage, and until the present canal system is perfected and extended 
but little development of the forest can be expected. The possibilities 
are suggested by the large shipments of logs, staves, headings, etc., 
from the Yazoo basin, where there was practically no lumber industry 

1 The Mississippi is estimated to carry to the Gulf of Mexico enough land waste to cover 
a square mile 268 feet deep, an amount of material that would require a train of 44 loaded 
cars arriving at the Gulf every minute, the specific gravity of the sediment being taken at 
2.5 and the capacity of a railroad car being 50,000 pounds. (J. E. Carman, The Mississippi 
Valley between Savanna and Davenport, Bull. 111. State Geol. Surv. No. 13, 1909, p. 23.) 

2 R. M. Brown, The Protection of the Alluvial Basin of the Mississippi, Pop. Sci. Mo., 
Sept., 1906, pp. 248-256. See also W. S. Tower, The Mississippi River Problem, Bull. Geog. 
Soc. Phil., vol. 6, 1908, pp. 83-100. 



ATLANTIC AND GULF COASTAL PLAIN 



527 




20 10 80 120 160 

Fig. 210. — The lower alluvial valley of the Mississippi. 



528 FOREST PHYSIOGRAPHY 

until the present levee system was constructed, the floods reduced, and 
swamp drainage begun. 

At the northern end of the lower alluvial valley of the Mississippi are 
two main belts of lowland separated by a long ridge of varying width. 
The two lowlands are joined across the ridge by a broad belt of lowland 
and by several narrow stream valleys. The lowlands are called the 
Advance (west) and the Cairo (east) lowlands, Fig. 210. The Advance 
lowland is essentially a unit, while the Cairo lowland is divided into two 
subordinate belts by a long ridge known as the Sikeston Ridge. The 
Advance lowland is from 2 to 8 miles wdde and is bordered in many 
places by relatively steep bluffs. The surface deposits of the lowland 
are sand and clay. A few long, low, flat-topped, sandy "islands" lie 
upon it at various places and furnish the only bits of land favorable for 
agriculture. 

The Cairo lowland on the east is nearly level and is bordered by 
prominent bluffs. The surface deposits consist of sand and silt, and on 
both this and the Advance lowland are numerous sloughs containing 
varying amounts of water. The small streams draining both lowlands 
have banks so low that they overflow during ordinary floods and the 
land is often submerged. The ridge between the two main lowland 
belts varies in height, form, and material, and is broken into a number 
of isolated sections. The main ridge extends southwestward, and to it 
the general name of Crowley's Ridge has been given. At its broadest 
part Crowley's Ridge is about 20 miles wide. Its upper surface is 
generally in the form of a rolling plain sloping gently westward. All 
the creeks flowing upon it have broad flood plains, with high land only 
in the form of narrow ridges on the main and secondary divides. On 
the main divide the valleys are deep and narrow and the surface 
maturely dissected. The eastern side of Crov/ley's Ridge is a definite 
and steep bluff throughout; the western edge is not so definite, only a 
part of its course being marked by bluffs. 

The western lowland (Advance) was once occupied by the Mississippi River. The eastern 
lowland (Cairo), once occupied by the Ohio River, is now occupied by the Mississippi. The 
change of course in the Mississippi was brought about through stream capture by tributaries 
of the Ohio working westward into Crowley's Ridge. A second capture of the Mississippi 
took place at a later time and brought about a further adjustment. The length of the valley 
abandoned by the first change of the Mississippi was more than 200 miles; the second change 
effected an abandonment of about 50 miles. The second change took place so recently that 
the river has not yet had time to clear its channel of rocks, much less to form a flood plain. 
The first change in the Mississippi brought its point of junction with the Ohio to a short 
distance south of New Madrid, Missouri; the second change brought it into its present relations 
with that river.' 

I C. F. Marbut, The Evolution of the Northern Part of the Lowlands of Southeastern 
Missouri, Univ. Mo. Studies, vol. i, 1902. 



ATLANTIC AND GULF COASTAL PLAIN 



529 



Louisiana- Texas Section 



The next section of the Coastal Plain extends from the Mississippi 
flood plain to the Rio Grande; the coastal margin of this section con- 
sists of wave-built ridges or reefs of exceptional continuity, Padre 
Island, south of Corpus Christi Pass, being 100 miles long. The lagoons 
back of these reefs are equally continuous; light-draft vessels may sail 
from the mouth of the Rio Grande through the Laguna de la Madre and 
through shorter sounds to Matagorda, 250 miles away. The depression 
of the coast is so rapid that the sand reefs are drowned and the lagoons 
are increasing in breadth. The combination of lagoons, fringing reefs, 
drowned river courses, complex est- 
uaries, and clean sea cliffs is an ex- 
pression of a sea advancing on a 
low-lying land, and the width of the 
belt in which these features are de- 
veloped is in a general way propor- 
tional to the rapidity of depression. 

The border of the plain is made 
up of alternating savannas and 
swamps or shoal bays. The low 
grounds are abandoned to reeds and 
sedges. The savannas are so low 
as to be clothed only with coarse 
grass and dotted with scrub pine 
or palmetto. Broad, low, natural 
levees like those of the Mississippi 
occur throughout the savannas, and 
these are commonly wooded, while 
the interstream tracts are prairie 
lands. Narrow belts of forest thus 
occur along the waterways except 
where the surface has been cleared 
for agriculture. Along Red River are well-wooded tracts with oak and 
hickory on the uplands, poplar and liquid amber on the lowlands, cypress 
and tupelo in the swamps. 

In the coastal plain of Louisiana the rivers are steep and sluggish, 
such as Vermilion Bayou, Calcasieu River, etc. Each of these streams 
is narrow, deep, and clear, has scarcely any current, expands into a 
broad shallow lake, and enters the Gulf through a shallow bay. All 
of them have features characteristic of drowned streams. In south- 




[. — Coastal features of Texas, long, simple 
sand reefs enclosing narrow lagoons. 



53© FOREST PHYSIOGRAPHY 

eastern Texas the streams of the Coastal Plain are similar to those 
of Louisiana; but west of the Nueces the coast drainage fails almost 
absolutely, the whole stretch of the coast to the Rio Grande containing 
only two small creeks. Though the greater part of the Louisiana-Texas 
section of the Coastal Plain is crossed by large rivers, a considerable 
part of the surface is poorly drained. Water stands in a multitude of 
small lakes or ponds throughout the year and there are large tracts 
covered with water during the wet season. 

The innermost belt of country belonging to the Coastal Plain rises 
rather rapidly from the adjacent seaward belt and has a more broken 
surface with numerous, small, rounded hills. The general elevation of 
this belt does not exceed 175 or 200 feet above sea level. The surface 
is in general timbered.^ 

SOILS AND VEGETATION 

In Texas the Coastal Plain consists of a western sandy subdivision 
and an eastern clayey subdivision; the line of separation is the Guad- 
alupe River in Victoria County. Soil distinctions while of great im- 
portance to vegetation in the interior of Texas are of little importance 
on the low Coastal Plain, where the chief consideration in tree growth is 
the water supply. The outer margin of the eastern and clayey subdivi- 
sion is swampy and flat and but little above sea level. Patches of sandy 
land occur on the borders of the clay area. Forests of pine, oak, and 
magnolia fringe the northern border of the coastal plain on the higher 
grounds, various species of gum occur on the benches, and heavy forests 
of black and red cypress are found on the low river flood plains. The 
greater part of the Texas section of the Coastal Plain consists of groups 
of prairies separated by forest tracts. 

One of the most interesting forest trees of the low coastal margin is 
the loblolly pine, which grows on slightly elevated mounds of the Texas 
lowlands where it forms forest islands. The surrounding prairie is 
covered with water several months each year and is wet nearly the 
entire year, so that loblolly pine develops almost undisturbed by fires. 
The gradual filling in of the prairie by the loblolly groves causes the land 
to become drier, and strips of young growth bridge the space between 
groves and finally develop into large bodies of forest. The seeds of 
the loblolly are scattered partly by the wind in a southeasterly direction 
if they ripen at the end of September or early October when northwest 
winds prevail, and partly by the southeastward drainage toward the 
Gulf during periods of high water. The drying up of the prairie and 

1 Hayes and Kennedy, Oil Fields of the Texas-Louisiana Gulf Coastal Plain, Bull. U. S. 
Gaol. Surv. No. 212, 1903, pp. 10 ff. 



ATLANTIC AND GULF COASTAL PLAIN 53 1 

the reclamation of the land is a natural process common to the whole 
coast of Texas and Louisiana. The swamp vegetation adds by its 
decay to the surface material and gradually the surface is built up- 
ward to the point where shrubs and trees come in. The process is 
rapid enough to cause marked changes in the distribution of timber in 
40 or 50 years, so that the marshes within the loblolly pine forest of 
eastern Texas, which a few years ago were impassable, are now acces- 
sible to man and to cattle.^ 

Southward from San Diego the Coastal Plain is composed of a belt 
of brown sand probably 25 miles in width. It is a rolling country 
more or less covered with mesquite and chaparral. Still farther south 
is a gray sand belt having a width of 50 or 60 miles and, except for a 
few live oaks, practically without trees. It has been called the Great 
Texas Desert, and across the face of it stretch two belts of moving sand 
hills in an east- west direction. Each belt consists of a double row of 
dunes from a half mile to a mile apart, moving westward under the 
prevailing easterly winds. Some of them (northern Star County) 
are from 90 to 100 feet high, but the size of the dunes decreases east- 
ward and near the coast they appear only as white spots lying but 
slightly above the plain. Some of them are almost circular with a 
central depression, others are oval, and still others are in the form of 
great crescents, the typical symmetrical dune shape. The dunes are 
composed of extremely fine sand of snow-white color, and the lightest 
wind sets the fine grains in motion. In several instances tall live oaks 
have been buried so deeply that only the dead tops of the highest 
branches indicate the fate of the groves invaded by the dunes.^ 

From one to two hundred miles west of the coastal tract the forests dis- 
appear or occur chiefly in the form of scraggly growths of blackjack and 
Chickasaw plum. Still farther west the mesquite is found in low orchard- 
like groves on the interfluves, with hackberry and acacia along the 
streams. Eventually these forms give place to the sage and the cactus 
of the deserts, except where the fertilizing streams have led to reclama- 
tion or support a more prosperous native growth. 

PHYSIOGRAPHIC DEVELOPMENT 

The structure and physiographic history of the Coastal Plain of 
Louisiana and Arkansas bear such an intimate relation to the major 
topographic features that a word in regard to them is necessary at this 

I R. Zon, Loblolly Pine in Eastern Texas, Bull. Forest Service, U. S. Dept. Agri., No. 64, 
1905, pp. 9-10. 
- Idem, p. 16. 



532 



FOREST PHYSIOGRAPHY 



place. In the Arkansas-Louisiana district the relatively soft formations 
of Cretaceous and Tertiary age which form the Coastal Plain overlie 
a peneplain developed upon older and greatly deformed strata. 

In Miocene and early Pliocene times erosion was active at a level distinctly lower than that of 
the old peneplain and resulted ultimately in the formation (late Tertiary) of local base-leveled 
surfaces, essentially coincident with the Coastal Plain and continuous with an uneroded outer 
area lifted so slightly above sea level as to suffer no important modification during this ero- 
sion period. This Tertiary base-leveling while extensive was not complete, and many rem- 
nants of the older and higher surface still project above the common level. 

After the partial development of a Tertiary peneplain there came a 
depression of the entire region of sufficient amount to allow the forma- 
tion partly by river aggradation, partly by marine deposition, of a great 
blanket of silts, sands, and gravels (the Lafayette formation) , which still 
occurs widely distributed throughout the region, its materials forming the 
surface soil to a large extent.^ 

The process of excavation of the material constituting the Coastal 
Plain has gone on with but one interruption since the deposition of 




The Lockesbure. Saratoga, Sulphu 
and Kisatchie wold:. 



Plood-Dlain and 
terrace area*. 



Fig. 212. — Prominent topographic features of the Gulf Coastal Plain in northern Louisiana and southern 
Arkansas. (Veatch, U. S. Gaol. Surv.) 

the Lafayette formation. Through either climatic change or crustal 
deformation or both the streams of the region after cutting out valleys 
began to aggrade their valley floors, but after the partial filling of the 
valleys reexcavation was begun. The result is that the streams are 

1 A. C. Veatch, Geology and Underground Water Resources of Northern Louisiana and 
Southern Arkansas, Prof. Paper U. S. Geol. Surv. No. 46, 1906, p. 46. 



ATLANTIC AND GULF COASTAL PLAIN 



533 



generally intrenched below the level of the upper 
surface of the alluvium which now occurs in 
terrace form fringing the borders of the valleys 
and constituting an intermediate level of bench 
land of considerable extent between the general 
surface of the Coastal Plain and the flood plains 
of the streams. 

Besides the terrace and flood-plain areas are 
extensive areas of upland that are interesting 
chiefly because of the development of alternat- 
ing belts of higher and lower lands in the form 
of cuestas and inner lowlands. The best de- 
velopment of these features is in Arkansas and 
Louisiana where there are four more or less per- 
sistent cuestas that follow the general strike of 
the formations. The three northerly ones are 
the Lockesburg, Saratoga, and Sulphur cuestas; 
the southernmost is distant from the other three 
and is called the Kisatchie cuesta. It is formed 
on the outcrop of the hard sandstone forma- 
tions known as the Catahoula (Oligocene), which 
have been brought to the surface and exposed 
by a fault, so that the cuesta is not a typical 
one but should be regarded rather as a modified 
fault scarp very similar, however, in its topog- 
raphy to a cuesta formed by ordinary dift'eren- 
tial erosion. Fig. 213. The Sulphur cuesta is 
formed on the harder members of the lower 
Eocene, and the Saratoga and Lockesburg cues- 
tas on the Cretaceous. 



3jnq^ai(0Oi 1 



4iodaA9jqs 



Oh > 



O ^ 



.S -^ 



SPECIAL FEATURES 



Tw^o important local features merit description 
at this point, for they constitute notable depart- 
ures from the normal types of topography and 
drainage with which we have so far had chiefly 
to deal. These are (i) the two types of mounds 
which exist in the district and (2) the lakes at 
the lower ends of the tributaries of the Red 



534 FOREST PHYSIOGRAPHY 

River. The first type of mound occurs in valleys where erosion has 
revealed the presence of domes with steep marginal dips attributed to 
igneous intrusions which did not reach sufficiently far toward the surface 
to be exposed by erosion. Only the top of the dome has been removed, 
and the topographic expression is commonly not a mound but a depres- 
sion rimmed about by harder limestone, from beneath which the softer 
formations have been removed by erosion. 

The second type of mound is not only a structural upHft but also 
a topographic elevation and has an extremely wide distribution, being 
well developed on the prairies and pine flats along the coast of Louisi- 
ana and Texas, where are found the "pimple prairies" popularly but 
erroneously associated with the oil deposits. They occur irregularly 
throughout the Coastal Plain and are best developed along the river 
terraces, though they are frequently found on the upland as well. No 
satisfactory theory has yet been formulated to account for them. On 
account of the wide distribution and unsettled character of the problem 
they represent, a partial bibliography of references is given at this point 
for the convenience of the reader. The different theories are discussed 
at some length by Veatch,^ from whose paper the following list of refer- 
ences is taken.- 

RED RIVER RAFTS 

Peculiar interest attaches to the great rafts of the Red River Valley 
on account of the unique combination of conditions which they repre- 
sent and the important changes they have effected in the hydrography 
of the Red River and its tributaries. The name raft is applied to the 
natural accumulations of timber along the river caused by the caving 
of the banks on the outside of the river bends. The main raft of the 
river began or at least was first known at Natchitoches, a town located 
below the raft and at the head of navigation. This was known as the 
Great Raft, and it grew steadily upstream with the constant addition of 

1 A. C. Veatch, Geology and Underground Water Resources of Northern Louisiana and 
Southern Arkansas, Prof. Paper U. S. Geol. Surv. No. 46, 1906. 

2 John C. Branner, Science, n. s., vol. 21, 1905, pp. 514-515; E. W. Hillgard, idem, pp. 
551-552; W. J. Spillman, idem, p. 632; A. H. Purdue, idem, pp. 823-824; and C. V. Piper, idem, 
pp. 824-S25. Branner and Purdue suggest that these mounds may represent immense con- 
cretionary formations. Spillman refers certain mounds in southwest Missouri to unequal 
weathering of limestone containing large chert masses. Branner gives many references to the 
mounds of the Pacific coast, for which he states the following theories have been advanced: 
(i) surface erosion, (2) glacial origin, (3) aeolian origin, (4) human origin, (5) burrowing 
animals, including ants, and (6) fish nests exposed by elevation. D. I. Bushnell, Jr., Science, 
n. s., vol. 22, 190S, pp. 712-714, has suggested the human origin theory, and this phase of the 
matter has been discussed by Veatch, Science, n. s., vol. 23, igo6, pp. 34-36. 




g. 214. — One of the timber jams composing the great Red River raft In buch a jam silt accumulates 
very rapidly and effectually fills the channel. (Veatch, U. S. Geo!. Surv.) 




Fig. 213. — Lakes of the Red River valley in Louisiana at their fullest recorded development. 

(Veatch, U. S. Geol. Surv.) p. S35 



536 



FOREST PHYSIOGRAPHY 




Fig. 216. — Timber deadened in temporary raft lake which was drained by the removal of the raft. 

(Veatch, U. S. Geol. Surv.) 




Fig. 217. — One of the Red River rafts after partial recutting of filled channel, 1873. 
(Veatch, U. S. Geol. Surv.) 



ATLANTIC AND GULF COASTAL PLAIN 



537 



material in that direction until in the latter part of the fifteenth cen- 
tury it had reached a point near iVlexandria. The effect of the natural 
dam which the raft created was to raise the level of the river on the 
upstream side of it and cause a ponding not only of the main river but 




Fig. 218. — Showing diversion of Red River below Alexandria, La., and location of rapids. Map also 
shows typical drainage features in the Red River and Mississippi River flood plains. (Veatch, U. S. 
Geol. Surv.) 



also of the tributaries within the reach of the ponded portion of the 
main stream. In some cases the rise of water in the main stream was 
sufl&cient to cause it to discharge about the natural dam and through 
the timbered bottom lands on one side or the other. Driftwood would 
be quickly accumulated about the new point of discharge and again the 



538 



FOREST PHYSIOGRAPHY 



channel would be shifted. At the end of about 200 years (estimated) 
the lower part of the raft began to decay and the front of it to move 
upstream as a great irregular accumulation of log jams and open water 

about 160 miles in length. 
Its average rate of advance 
was about four-fifths of a 
mile a year during the 
period between 1820 and 
1872, though the rate was 
intermittent and to a large 
extent dependent upon the 
discharge of the stream 
from year to year. 

As the head of the raft 
moved upstream it blocked 
all the tributary streams 
in succession and caused 
the formation of lakes at 
the points of junction with 
the main stream. In sim- 
ilar fashion the tributaries 
that were freed by the 
decay and retreat of the 
raft material along the 
front of the raft again 
discharged in the normal 
way and proceeded to dis- 
sect the deposits that had 
been accumulated on the 
floor of the temporary lake 
at their mouths. 

Since the removal of the rafts 
from the Red River the water has 
gradually resumed its old level. 
From 1873 to 1892 the river had 
lowered its bed about 15 feet at a 
point above Shreveport; the lake 
areas are rapidly draining and the 
extensive lake system along the 
course of the Red River shown on most maps is practically nonexistent. The continuance of 
some of the lakes and the occurrence of rapids and small falls in some of the tributaries are due to 
the drainage deflections that resulted from the silting up of the floors of the temporary lakes and 
the assumption of a new channel by the recreated stream. Superposition was inevitable under 




Fig. 219. — Growth and drainage of the raft lakes at the Arkansas- 
Louisiana state line. (Veatch, U. S. Geol. Surv.) 



ATLANTIC AND GULF COASTAL PLAIN 539 

these circumstances, the stream in certain instances flowing over projecting and now covered 
Tertiary spurs that have been revealed by erosion. The most notable instance of such diver- 
sion is in the case of the Red River itself, which has rapids immediately above Alexandria. 
The main features are shown on Fig. 218. 

Soils 

Although the soils of the various districts of the Coastal Plain have 
been incidentally mentioned in the discussion of topographic and drain- 
age features, a connected description of their qualities is essential in 
understanding their geographic distribution and origin. 

The soils of the Atlantic and Gulf Coastal Plain are for the most 
part composed of sands and light sandy loams, with occasional depos- 
its of silts and heavy clays. The heavy clays are found principally 
near the inner margin of the Coastal Plain. The silts, silty clays, and 
black calcareous soils upon which the rice and sugar-cane industries of 
southern Louisiana and Texas are developed have no equivalents in the 
Atlantic division. Differences in the method of deposition, subsequent 
erosion, and drainage conditions are responsible for a great diversity of 
soil types with complicated relationships. 

The following are the most important series that have so far been recognized: (i) Light- 
colored sandy soils underlain by yellow or orange sand or sandy clay subsoils. Where the drain- 
age is insuiEcient, the subsoil is often mottled. With few exceptions these are special-purpose 
rather than general farming soils, and constitute the most important truck soils of the coastal 
plain. (2) Dark -gray to black surface soils, underlain by yellow, gray, or mottled yellow and 
gray subsoils. The dark color of the soils is due to an accumulation of organic matter during 
an earlier or existing swampy condition. TIms series is intermediate between the light-colored 
soils on the one hand and the peat and swamp areas on the other, and occupies depressed areas, 
or areas so flat that the water table is at or near the surface, except where the country is 
artificially drained. In this series the fine sandy-loam type supports a heavy growth of 
cypress, gum, magnolia, and other water-loving trees and undergrowth. It is characterized 
by level or slightly depressed surface features. Lack of drainage is responsible for the ex- 
istence and peculiar characteristics of the type. In most cases artificial drainage is imprac- 
ticable, owing to the low gradient. 

(3) A third series is derived largely, but not entirely, from the Lafayette mantle of 
gravels, sands, and sandy clays. The surface soils are usually gray to brown in color and are 
invariably underlain at a depth of 3 feet or less by a red or yellowish-red sandy clay. The 
prevailing red color of the subsoil is the characteristic feature. (4) A fourth series includes 
the barrier islands or bars, shore-line deposits, and low-lying marshes of the immediate coast 
line. The barrier bars consist of sand accumulated by wave action and further modified by 
winds. The soils of the marshes, consisting of sandy loams, loams and clays, have been built 
up by the deposition of silt and clay carried in by streams, by wind-blown sand from the ad- 
joining sand areas, and by the decay of coarse salt grasses and other native vegetation. The 
agricultural value of these lands is very low, depending mainly upon pasturage and the coarse 
hay, and they are a distinct menace to health, as they form the breeding places of disease- 
carrying insects. Efforts to drain and reclaim these marshes have been attended with some 
success. The possibilities of successful reclamation depend upon the keeping out of the tides 
and the subsequent efficient drainage of the land. 

(5) The soils of the black, calcareous prairie regions of Alabama, Mississippi, and Texas are 
characterized by a large percentage of lime, especially in the subsoil, which in some of the 



540 FOREST PHYSIOGRAPHY 

types consists of white, chalky limestone. They have been derived from the weathering 
of calcareous clays, chalk beds, and "rotten" limestones (Cretaceous). In some localities 
remnants of later sandy and gravelly deposits have been mingled with the calcareous material, 
giving rise to gravelly and loamy members. The soils are very productive and are at present 
devoted chiefly to the growing of cotton and corn. 

(6) The next series includes dark-gray soils found upon gentle slopes or undulations adjacent 
to streams and upon level or depressed areas in the uplands. Their formation is due largely 
to the peculiar topographic conditions resulting from the sinking of the limestones which 
underlie, in some of the areas, the materials from which other soils have been derived. They 
may be considered as colluvial soils formed by the creeping or washing of material from higher- 
lying areas. The sandy type has a considerable admixture of organic matter and lies on gentle 
slopes or undulations adjacent to streams. It is mainly hammock land, supporting a growth 
of hardwood forest, and is very productive. 

(7) A series consisting of gray and brown surface soils underlain by heavy, plastic, red, 
mottled subsoils. Where the basal clays are exposed by erosion they show brilliant colorings, 
often arranged in large patches of alternating liver-color, red, and white. These clays are 
remarkably plastic and constitute the oldest marine deposits along the inland margin of the 
Coastal Plain. The soils are usually of low crop-producing capacity and are covered chiefly 
with pitch pine, scrub oak, and other trees of little commercial importance.^ 

Tree Growth of the Coastal Plain 

The special vegetal features of the various sections of the Coastal 
Plain have been described in the foregoing pages. It remains to note 
certain general features more or less common to the whole province. 
Two points are of chief interest in this connection: (i) the effects of 
water supply and (2) the effects of texture and chemical properties on 
the native vegetation. Speaking in general terms one may say that the 
Coastal Plain exhibits (i) a number of inner belts more or less clayey 
in character and heavy, (2) a broad expanse of sandy land forming the 
long outer slope of the plain and almost all of the so-called upland, 
(3) river bottom lands fringed in many places with terraces or higher 
lands called "second bottoms" or hammocks, (4) a border of marshy 
land consisting of fresh-water marshes on the landward side and of 
salt-water marshes on the seaward side, and (5) a line of long, narrow 
reefs but little above high tide except where blown by the wind into 
higher sand dunes. 

The reefs are for the most part sandy, though coral reefs fringe a 
part of the coast of Florida and some of the reefs of the Gulf region are 
covered with shells accumiulated by the Indians. The sand reefs gen- 
erally bear a growth of pine which may be of good quality as originally 
on the reefs of North Carolina, or it may be stunted and mixed with 
low, gnarled cedar, etc., as on many of the reefs of New Jersey and 
Texas. The shell hammocks of Alabama and Mississippi are not re- 
stricted to the reefs but are found also on inlets and bayous easily 

I Soil Survey Field Book, U. S. Bur. of Soils, igo6. 



ATLANTIC AND GULF COASTAL PLAIN 541 

accessible to the water. Pitch pine, hve oak, red cedar, sweet gum, and 
prickly ash are the most common shell-hammock trees. 

On the marshes and wet pine barrens the deciduous cypress {Tax- 
odium imbricarium) and the common swamp cypress are the ordinary 
growths along a large part of the coast line. In addition many of the 
smaller marshes have a growth of stunted pine, maple, and black gum. 
The bottom lands along the rivers, the "first bottoms," generally have 
a stiff heavy soil with an excess of water and are subject to overflow. 
Their timber is generally luxuriant and consists of chestnut, white oak, 
sweet gum, black gum, magnolia, bottom white pine, cypress, black 
walnut, tulip, hickory, and ash. Among these the black and the sweet 
gums are most numerous and characteristic, hence the name " gum 
swamps " commonly applied to the bottom lands. The second bottoms 
or hammock lands are slightly higher than the first bottoms, are never 
overflowed, have a silty not a clayey soil, and have a poorer tree growth, 
among which the most common types are white oak, water oak, bottom 
white pine, magnolia, iron wood, post and black-jack oaks, willow oaks, 
etc., all more or less stunted and scattered in their growth. 

The upland trees are economically of greatest importance and are 
at the same time most interesting from the ecologic standpoint. The 
great sandy expanses of the outer slope of the Coastal Plain are covered 
mainly with longleaf pine. The seaward margin of the sandy belt is, 
however, level prairie in most cases, on which the trees are disposed in 
clumps or groves. In Texas the islands of higher lands are covered 
with loblolly pine. In Louisiana groves of honey locust, red haw, and 
live oak dot the outer prairie region. Inland from the great longleaf 
pine belt the calcareous layers of the Coastal Plain outcrop and are 
covered with a distinctive and for the most part a lime-loving vege- 
tation. Oak and shortleaf pine are the most important types; mixed 
with them are red cedar, red haw, crab-apple, and honey locust. It is 
noteworthy that the heaviest clay soils on the inner margin of the 
Coastal Plain of Texas, Louisiana, Mississippi, and Alabama are marked 
by large numbers of prairie tracts alternating with groves of stunted 
trees, mostly red cedar, Chickasaw plum, and scrubby post and black- 
jack oaks. 

The most unproductive soils occur on the so-called ridge lands 
toward the inner margin of the Coastal Plain where some of the ridges 
are developed on the outcrop of sandy formations. Scarlet and post 
oak, black-jack oak, and stunted pines are the principal trees. They 
are characteristic growths on all the more infertile phases of the coastal- 
plain soils. The calcareous soils, by contrast, are notably fertile and 



542 FOREST PHYSIOGRAPHY 

have a good growth of hickory, ash, sweet gum, and honey locust. So 
faithfully do the distributions of these types follow the outcrops of the 
respective formations that a vegetation map on the one hand, and a 
soil map or a geologic map on the other, show striking correspondences 
in the positions of the boundary lines.^ 

1 For a description of the tree types of the Coastal Plain in Texas see R. M. Harper, Contr. 
Dept. Bot., Colum. Univ., Nos. 192, 215, 216, 1902-1905; for the timber belts of the Coastal 
Plain in Texas see W. L. Bray, Forest Resources of Texas, Bull. U. S. Dept. Agri., Bur. For. 
No. 47, 1904; for the trees of Mississippi see E. W. Hilgard, Geology and Agriculture of Miss. 
i860, and Soils, 1906, Chaps. 24 and 25; for Alabama see Charles Mohr, Plant Life of Ala- 
bama, Ala. Gaol. Surv., 1901. 



CHAPTER XXVI 

PENINSULA OF FLORIDA 
General Geography 

The peninsula of Florida is remarkable for its projection southeast- 
ward into the Atlantic Ocean for 350 miles, its smooth, well-developed 
eastern shore line, its great keys and swamps, and its slight relief. It 
ranges in altitude from sea level to 200 feet above the sea at various 
points on the broad flat-topped tract which forms the center of the 
peninsula and to about 300 feet in the northwestern counties of Florida. 
A depression of 50 feet would cover all of southern Florida except the 
tops of sand hills and ridges, while an elevation of 50 feet would extend 
the shore line westward 20 miles from Cape Romano and make dry 
land of Biscayne Bay and Bay of Florida. 

The northern and western parts of Florida consist of a narrow, deeply 
eroded limestone (Vicksburg) upland which descends southward rather 
abruptly to a low coastal region and northward by more gentle 
descents to the adjacent Coastal Plain. The rivers of the northern 
region are consequent upon the initial slopes of the land as it emerged 
from beneath the sea except where they have removed the thin mantle 
of surface sand and superimposed themselves upon the older strata 
beneath. The southern and central portions of Florida form a great 
lake and swamp district, the lakes occupying sinks or depressions in the 
underlying limestones or shallow and broad depressions in the surface 
of the deposits overlying the limestones. Extreme irregularity of out- 
line characterizes the shores of the lakes and extreme irregularity of 
direction the courses of the rivers. Many streams of the peninsula 
have their sources in springs that occupy underground courses in the 
limestone. These bring to the surface large quantities of mineral 
matter, and it has been estimated by Sellards ^ that the rate of solution 
is sufficient to remove about 400 tons per square mile per year, an 
amount which would lower the surface of the limestone about i foot in 
5000 to 6000 years. The underground passages are sometimes several 
hundred feet in diameter and several miles in length. The level char- 

1 A Preliminary Report on the Underground Water Supply of Central Florida, Bull. 
Florida State Geol. Surv., No. i, 1908, p. 16. 

543 




S44 



Fig. 220. — Principal lakes and coastal features of Florida. 



PENINSULA OF FLORIDA 545 

acter of the surface and the porous soil which mantles the bedrock 
afford an excellent opportunity for the formation of caverns, since they 
result in a large absorption of the heavy rainfall. The sink holes are 
in process of formation to-day and instances are known where sinks 
have been formed by the collapse of cavern roofs in different parts of 
the lake region. The same process has resulted in the formation of 
many natural bridges, as those of northern Walton County, at St. Marks 
River, and Santa Fe River. 

Geologic Structure 

In respect of structure Florida is an elevated crust block modified by 
a number of minor folds. ^ The present peninsula is regarded as rest- 
ing on a much more extensive foundation of Eocene limestone, forming 
a plateau which formerly extended from the southeastern margin of 
the continent to Cuba and the Bahamas, and possibly to Yucatan. The 
isolation of the peninsula may possibly be due to faulting, and in part to 
current scour. In a number of places are gentle folds whose axes are 
generally parallel with the trend of the peninsula; these succeed one 
another in series between Lake Okechobee and Gulf of Mexico.^ One 
such fold is near the Atlantic coast, another near the Gulf coast, and 
a third in the vicinity of Brooksville and Plant City. The eastern 
ridge includes the well-known Trail ridge and forms the eastern bound- 
ary of the central lake basin. The western ridge forms the western 
boundary of this basin and passes through Lakeland.* 

Physiographic Development 

Recent stratigraphic studies have determined the fact that the Flo- 
ridian region was outlined in somewhat its present form in pre-Oligocene, 
probably Eocene time, but that it then existed in the form of a shallow 
submarine platform swept by ocean currents and blanketed by both, 
organic and terrigenous deposits.^ During the time between this early 
period and the final emergence of the crust-block as a peninsula the region 
was subjected to many changes of level — a series of four emergences and 
a corresponding number of submergences. During the progress of these 
changes the surface of the platform was never carried far below and 
never far above sea level. The submergences were usually about 100 
feet and never more than 200 feet, while the latter figure expresses the 

t W. H. Dall, Neocene of North America, Bull. U. S. Geol. Surv. No. 84, 1892, pp. 85-87. 
» Idem, p. 88. 

' Matson and Clapp, 2d Ann. Rept. Fla. Geol. Surv., igog, p. 48. 

* T. W. Vaughan, Sketch of the Geologic History of the Floridian Plateau, Science, n. s., 
vol. 32, 1910, pp. 24-27. 



546 FOREST PHYSIOGRAPHY 

maximum elevation above sea level, a maximum that was attained 
during the Pliocene emergence. It was the fourth Pliocene emergence 
that gave the peninsula the outline that it has to-day. In the time 
since then the living coral reefs have developed, the Everglades have 
been formed, and the shores given their detailed characteristics. The 
net result of all the changes of level has been to leave the eastern side 
of the peninsula higher than the western and to bring into existence a 
number of small low folds whose axes run north-south in sympathy 
with the main axis of the peninsula. The Kissimmee River for example 
occupies an anticline flanked on both sides by low anticlines. 

Topography and Drainage 

Although the mainland of Florida has slight relief it exhibits a con- 
siderable variety of topographic types, and since even small differences of 
elevation have a marked effect on the vegetation, it is possible roughly 
to divide the mainland of the peninsula into districts whose topographic 
features are intimately related to the vegetal growth. On this basis 
Florida may be divided into pineland and swamp. The pineland in- 
cludes "hammocks" — isolated elevated patches supporting hard- 
wood trees of several genera — and many prairie or grassy tracts. The 
swamps include the marshy borders of the inland lakes and the coastal 
swamps with their sedges and black or red mangroves. It must be re- 
membered, however, that this line of demarcation between swamp and 
pineland is extremely irregular and, on account of the low relief, varies 
with the seasons to a certain extent. 

The total area covered by pine forests is probably in round numbers 
300 square miles; on the east coast they extend in a narrow belt be- 
tween the Everglades and the coastal swamp from northern Palm 
Beach County to near Homestead. This belt is about 20 miles wide at 
the north, 6 miles wide near Jupiter Inlet, and from 2 to 8 miles wide 
towards the south. In northern Monroe County the pines grow in 
disconnected areas alternating with stretches of cypress.^ The pine- 
lands may be divided according to the relief into dunes, rolling sand 
plains, flat land, and rock ridges. 

DUNES 

The dunes of southern Florida lie near the coast and occur as a dis- 
continuous series of irregular mounds and ridges separated by inter- 
vals of flat or gently rolling country or by stretches of shallow water. 

' The best brief description of the topographic features of southern Florida and the one on 
which the following paragraphs are chiefly based is by S. Sanford, 2d Ann. Rept. Fla. Gaol. 
Surv., pp. 177-231, where the results of many other investigators are assembled. 



PENINSULA OF FLORIDA 547 

They seldom reach more than a few miles inland and but rarely face the 
ocean. An important group of dunes are those that occur near Jupiter 
Inlet at West Palm Beach, and on the east side of Lake Osborn. On the 
west coast of Florida there are few dunes south of the Caloosahatchee 
River. The dunes are not in movement to-day, and there is no lee- 
ward march which overwhelms trees and threatens dwellings as at Cape 
Henry, Virginia, and on Hatteras and Currituck Banks in North Carolina. 
When cleared of pine timber and palmetto scrub they may be utilized 
in the growing of tropical fruits. 

ROLLING SAND PLAINS 

The rolling sand plains include sandy stretches of the mainland with 
broad swells ahd low ridges, the swells being occupied by shallow lakes 
or lagoons and wet prairies or cypress swamps. On the east these sand 
plains form a belt with a maximum width of 6 miles and extend from 
the north side of Palm Beach County nearly to the Miami River and 
merge inland into the monotonous level of the flat lands and prairies 
bordering the Everglades. On the seaward side they are bounded by 
swamps ; on the east coast the higher ground and the ridges are frequently 
covered with a straggling growth of spruce pine. In the hollows are 
many fresh-water lakes, som.e of which are several miles long. Most of 
them are less than 10 feet deep and some are so shallow that they entirely 
disappear during seasons of deficient rainfall. The rolling sand plains 
are believed to be the result of wind action and to constitute but a 
broader development of the present dune topography near the coast. 

FLAT LANDS 

The name "flat lands" is used to designate the imperfectly drained 
pinelands lying between the narrow belt of rolling sand plains and the 
Everglades and their bordering prairies. The soil is a white sand 
which bears a thin growth of pine trees, with many prairie expanses 
a mile or more wide. In the rainy season these prairies are shallow 
lakes. There are also a number of sloughs and shallow ponds that 
in places support good growths of c)rpress, the pine and cypress often 
intermingling in very irregular fashion. On the west side of the lower 
end of the peninsula the surface between the Everglades and the Gulf 
is even more monotonously level than on the eastern coast, and the re- 
lations of swamp and dry land are more irregular. Much pine occurs 
in patches and strips separated by cypress swamps, a combination often 
designated as "pine islands and cypress straits." In places prairies 
are scattered through or fringe the pinelands, and some of them make 
excellent cattle ranges. 



548 FOREST PHYSIOGRAPHY 

ROCK RIDGES 

This term is applied to those outcrops of solid rock that rise above 
the general flat expanse of country, though they may not rise more than 
2 feet above the general level and probably in no case does their ele- 
vation exceed 35 feet. Their extent is estimated at 200 square miles. 
On the east coast the rock ridges are of oolitic limestone and separate 
the great saw-grass swamp of the Everglades from the fringe of man- 
grove swamps and salt prairie along the western shore of Biscayne Bay. 
Even in the Everglades some of the keys have a rocky foundation, but 
the only ones which expose bare rock are Long Key and those related 
to it. On the west coast of Florida hard rock outcrops are more scat- 
tered than on the east coast, but cover a wider area, running through 
the pinelands in strips varying in length up to several miles; 

SWAMPS 
THE EVERGLADES 

The swamp land of southern Florida includes the great saw-grass 
morass of the Everglades, the cypress swamps about it, and the salt 
marshes and mangrove swamps of the coast. The most important 
swamp is of course the Everglades with its wide expanse of sedge, its 
broad strips of shallow water, its scattered clumps of bushes, its many 
islands, and its underlying limestone floor. The Everglades reach 
from Lake Okechobee on the north to Whitewater Bay on the south, 
and are 50 miles wide in their widest part. Their area is estimated at 
5000 square miles. ^ The border of the Everglades is well known, but 
the vast interior of water- and sedge-covered muck has been visited by 
few geologists and crossed by none. 

The Everglades tract lies in a huge shallow sink, or a series of more 
or less connected sinks.- Countless shallow ponds of clear water are 
found in which grow bulrushes, lilies, and other water plants, saw 
grass, flags, and cane. The Seminole name for the Everglades is 
"Grassy Water." Scattered here and there in the sea of grass are 
islands of bushes and trees, called keys, which owe their origin to accu- 
mulations of vegetable matter; and the slight relief of the region is 
brought out strikingly by the fact that such slight accumulations of 
material should produce islands of drier land. The whole region ap- 
pears to be very young; it is almost without soil or definite surface 
drainage. As a result of the slight relief there is no sharp dividing line 

1 L. S. Griswold, Notes on the Geology of Southern Florida, Bull. Mus. Comp. Zobl., 
vol. 28, 1896. 

2 A. Agassiz, The Elevated Reefs of Florida, Bull. Mus. Comp. Zo'61., vol. 28, 1896, p. 30. 



PENINSULA OF FLORIDA 



549 



between the Everglades and the surrounding country, and a difference of 
two feet in water level means the difference between shallow lake and 
dry land for hundreds of square miles. No two of the maps of Florida 
agree either in the number, position, or outline of the lakes of the Ever- 
glades because of the variation in these features with the height of the 
w^ater. Much of the eastern and northern shore of Lake Okechobee is bor- 
dered by cypress swamps, some of these containing the tallest cypresses 
to be found in Florida. On the east the Everglades are bordered by 




Fig. 



■Swamp lands of the United States with degrees of swampiness shown in two shadings. 
(Gannett, U. S. Geol. Surv.) 



prairie and cypress swamps; in a few places patches of hardwood grow 
on slight elevations on the western border of the Everglades. Here are 
low irregular elevations, measured by inches, that diversify the distribu- 
tion of water and sedge; here, too, are narrow winding sloughs some of 
which extend for miles. 

Lake Okechobee itself is drained by a canal through the saw grass to Lake Hicpochee and 
the Caloosahatchee River. It is also drained by a few short streams that flow southward 
from the southern edge of the lake but are closed up after a few miles by thick growths of saw 
grass. The flatness of the Everglades may be appreciated by the elevations as determined at 
different times, which run from 6 to 23 feet in various portions, and it has been stated that the 
damming up of the main canal on the west of Lake Okechobee by raising the water three 
feet inundated the marginal prairies on many of the east coast ridges and seriously hindered 
the growing of vegetables. Bedrock lies at or near the surface toward the edge of the Ever- 
glades, and near Miami the rock forms bare ridges with a maximum height of 15 feet above the 
sea. The depth to bedrock in the central portion of the Everglades is 3 or 4 feet, and the flat- 
ness is so great that the word "basin" is inappropriate in describing it. 



5SO FOREST PHYSIOGRAPHY 

COASTAL SWAMPS 

The coastal swamps include the wet lands along the lagoons or the 
so-called rivers back of the barrier beaches of the east coast. Many of 
the swamps on the east side support a scrubby growth of mangrove, but 
on the west side, especially in the Shark River archipelago and the 
southern part of the maze of land and water known as the "Ten 
Thousand Islands," the mangrove forms a notable forest, the trees 
reaching to a height of 60 feet or more, with green smooth trunks 
2 feet or more in diameter at the base and without limbs for 30 feet 
above the ground. The mangrove forest rises from the Gulf like a 
green wall and is one of the most striking features of the shore line of 
southern Florida. 

FLORIDA IS NOT A CORAL REEF 

The work of Agassiz and others has shown that the older and popular 
view that the peninsula of Florida is an elevated reef is incorrect; the 
thickness of the coral reef formed since Pliocene times is probably about 
15 feet, as determined by borings at Key West in 1895. Beneath the 
coral reef are Pliocene rocks, and beneath these in turn at a distance of 
700 feet are rocks of Eocene age. The coral reefs now visible on the 
seacoast have but a moderate development inland. An elevated coral 
reef of notable width constitutes the outer edge of the peninsula of 
Florida. It has been traced from 20 to 30 miles inland at some points, 
although in other localities it has a very much more limited occurrence. 
This great development of reef rock should not, however, obscure the fact 
that the interior of the peninsula is of totally different origin, consisting 
of limestone, chiefly of marine origin, although with certain aeolian 
facies. In the shore zone in which the reefs occur there are also found 
great patches of aeolian rocks filling intermediate sinks and alternating 
with patches of reef rock of variable extent.^ 

DRAINAGE FEATURES DUE TO KARSTING 

The drainage of Florida is characterized by the presence of large 
numbers of sloughs, shallow ponds, and lakes. The interior is chiefly 
swamp. Fig. 220, with no well-defined river systems or stream valleys, and 
in spite of the low elevation of the larger part of the peninsula the streams 
that flow from the Everglades into the Atlantic have rapids in their 
upper courses wherever bedrock occurs. The drainage irregularities 

1 The most comprehensive account of the geology and topography of the keys of southern 
Florida is by A. Agassiz, The Elevated Reef of Florida, Bull. Mus. Comp. Zool., vol. 28, 1896, 
pp. 29-63. 



PENINSULA OF FLORIDA 55 1 

are due in part to the irregularities of the beds that form the land sur- 
face and in part to their general features and slight elevation above sea 
level. Additional factors controlling the stream systems have been the 
extensive karsting^ of the limestone areas that underlie so large a portion 
of the state, with the production of many sink holes, underground chan- 
nels, caverns, etc. The higher portion of the state is honeycombed with 
underground passages, but these decrease in number on approach to 
the coast. No small part of the irregularities is probably due to the 
irregular manner in which the grasses grow, which in turn affects the 
distribution of land waste. 

The extreme irregularity which characterizes the drainage features of the peninsula of 
Florida must therefore be ascribed to three causes; first, the youthfulness of the entire surface 
and lack of time in>which the drainage might become organized and the lakes drained; second, 
to the extremely slight relief of the surface and the absence of any dominating slope, as in the 
Coastal Plain of the Atlantic region or the Great Plains of the central part of the United States; 
third, to the influence of the dissolving action of the ground water which proceeds in detail 
with almost a total disregard of the surface of the slopes of the land. The result is that un- 
derground water passages are opened from sink to sink and from lake to lake, oftentimes in 
opposition to the surface slopes, as in the celebrated case of the Danube and the Rhine in 
Europe, in which the upper part of the Danube is to a large extent absorbed by porous lime- 
stones, which in turn deliver the water to underground passages that lead to the Aach, a 
tributary of the Rhine system. The result is that the upper Danube belongs almost wholly 
to the Rhine system.^ To add to the complexity of such regions the covers of the under- 
ground channels are dissolved by percolating water to the point of collapse, passageways are 
blocked, and the waters rise to the upper level of the obstruction. In brief, it may be stated 
that the irregularities are in large measure due to the combination of surface and underground 
drainage systems which originate in different ways and v/hich to a large extent obey dif- 
ferent laws. 

COASTAL ISLANDS 

The islands that fringe southern Florida are of several types. Some 
are long, narrow, barrier beaches crowned with coconut palms and 
bordered by mangrove swamps; some are true mangrove islands that 
resist wave action; some are low-lying sand banks supporting a scanty 
growth of beach grass and weeds; and some are of rock that reaches 
above sea level, these being covered with scrubby hardwoods, palms, 
and pines. Within the outer chain of islands that fringe the mainland 
or dot the Bay of Florida are other keys in all stages of development, 
from banks below sea level to banks bare at low tide and covered with 
mangroves that arrest the movement of sand, seaweed, and driftwood, 
and contribute to the reclamation of the sea floor. 

The existing keys and islands south of the peninsula of Florida 
are regarded as once having been continuous or practically so. It ap- 
pears that a process of gradual disconnection has taken place between 

1 The name applied to the process that results in a karst topography, i.e., a topography 
marked by sink holes, underground channels, vertical shafts, etc., as developed on many lime- 
stone tracts and typically in the Karst Mountains of Austria. 

2 Petermann's Mitteilungen, igoy, and Natur WissenschaftHche Wochenschrift, 1908, No. 7. 



552 FOREST PHYSIOGRAPHY 

the Florida keys and the mainland proper. It is ascribed to the erosive 
and solvent action of the sea. The sounds may have originally been 
sinks similar to those of the Bahamas and the Bermudas, the action of 
the sea having broken through the barriers separating the s.ounds from 
the ocean. Once channels were formed the action of the sea would 
increase their width and depth, and the sea would thus gradually en- 
croach upon the floors of the sinks, forming more and more distinct 
sounds out of them, or even huge open bays like Key Biscayne Bay. 

The keys forming the small group immediately east of Key West, 
Fig. 220, have a northwest-southeast alignment. They are not coral 
reefs but are underlain by oolitic limestone which has an irregular sur- 
face more or less covered with marl and calcareous sand. The breaches 
between the islands are due to tidal currents caused by differences in time 
and height of the tides of the Gulf and the Strait of Florida'. The great 
curve of the sand reefs on the eastern coast is caused by longshore current 
action, the currents moving from north to south as an eddy between the 
Gulf Stream and the mainland. 

There is a bedrock floor of limestone in the Biscayne pineland on Long 
Key and on adjoining keys in the Everglades. The coast of this part 
of Florida is either stationary or sinking, but if sinking, the rate of 
depression is extremely slow. At the present time there is in progress 
an extensive reclamation of the sea by the accumulation of large quan- 
tities of shells of marine organisms and by the abundant organic life 
associated with the mangrove swamps of the coastal border.^ 

There is the utmost difference in the vegetal covering of the islands, 
due to slight differences in elevation and to differences in the character 
of the surface. In some places it is bare rock, in others rock with a thin 
veneer of sand, marl, and leaf mold, and in still others a cover of cal- 
careous sand. On low land near the water's edge mangroves are found, 
on the beaches coconut palms, on the low marl flats grasses and sedges, 
while the higher ground, called "hamm_ock, " supports a dense growth of 
scrubby hardwood trees, button wood, ironwood, madeira, etc., while on 
three keys patches of pine are found. The trees seldom reach a height 
greater than 20 feet. 

Soils and Vegetation ^ 

The widespread occurrence of Pleistocene sand as a surface deposit 
a few feet thick results in an intimate relation between the soils of the 

1 For an excellent description of these mangrove swamps, their great importance in the 
winning of lands from the sea, and their peculiar forms of vegetation, see N. S. Shaler, loth Ann. 
Rept. U. S. Geol. Surv., pt. i, 1888-9, PP- 291-295. 

2 The common and much more abundant types of vegetation are described in detail in 
connection with the topographic types with which they are so intimately related, pp. 546 to 
550. 



PENINSULA OF FLORIDA 553 

peninsula and this formation. Where erosion has been exceptionally 
active both the Pliocene and the Pleistocene deposits have been removed, 
leaving older geologic formations to form the soils, but such occurrences 
are relatively rare and unimportant.^ In the southern part of Florida 
and in isolated patches elsewhere in the state peat and muck soils 
occur. These have their greatest development in the Everglades. 
They consist of organic matter mixed with a certain amount of sand and 
clay and are of recent origin. Their occurrence is confined to low up- 
land areas with imperfect drainage. In the upland portion of the state 
the Lafayette formation is found as isolated areas but these are of little 
importance except as tobacco soils in the northwest. At various places 
along the east coast Pleistocene marls and coquina in a more or less 
decomposed state form the subsoil, and the same is true on the west 
coast south of Bradentown. The clay and loam soils cover a very' 
limited portion of Florida and are not of much importance. Clay 
soils are confined chiefly to small areas along the stream courses and are 
not tilled. The greater part of Florida has a sandy or sandy loam soil 
of low natural productivity but quickly responding to proper treatment. 
It is naturally deficient in moisture in spite of the rather abundant 
rainfall, and irrigation is practiced in a few places.^ Extensive drainage 
operations are in progress in the Everglades region which will ultimately 
mean the reclamation of large tracts of peat soil whose natural pro- 
ductivity is high and which is suitable for the production of a large 
variety of tropical fruits. 

Florida extends so far southward as to exhibit subtropical or antillean 
forms of vegetation. The subtropical belt encircles the southern half 
of the peninsula from Cape Malabar on the east to Tampa Bay on the 
west.^ The royal palm, Jamaica dogwood, manchineel, mahogany, and 
mangrove are among the uncultivated tropical plants, and the banana, 
coconut, date palm, pineapple, grapefruit, and cherimoya among the cul- 
tivated plants of this district.^ It is of interest to note here that the 
subtropical region enters the United States at two other points besides 
Florida — the lower Rio Grande region in Texas and the lower Colorado 
River Valley in western Arizona and southeastern California. 

1 Matson and Clapp, 2d Ann. Rept. Fla. State Geol. Surv., 1909, pp. 37-43. 

2 Idem, p. 45- 

' C. H. Merriam, The Geographical Distribution of Life in North America with Special 
Reference to the Mammalia, Proc. Biol. Soc. Wash., vol. 7, 1892, p. $3- 

^ C. H. Merriam, The Geological Distribution of Animals and Plants in North America, 
Yearbook Dept. Agri., 1894, p. 211; idem, Life Zones and Crop Zones of the United States. 



CHAPTER XXVII 

LAURENTIAN PLATEAU AND ITS OUTLIERS IN THE 
UNITED STATES 

Laurentian Plateau 



TOPOGRAPHIC FEATURES, 



The Laurentian Plateau includes all the country north of Lake 
Superior, Lake Ontario, and the St. Lawrence line, as far as Hudson Bay 
and the Arctic shore of Canada; east and west it extends from Lakes 




Fig. 222. — Chiefly metamorphic and igneous rocks within the heavy lines, chiefly sedimentary rocks 
without; the Laurentian peneplain is dotted. (Wilson.) 

Athabaska, Manitoba, etc., to the Labrador coast. Its boundaries are 
indicated on Fig. 222 and include about one million square miles 
of land. It embraces practically the whole northeastern section of 
North America. Two outliers of the province lie in the United States: 

554 



LAURENTIAN PLATEAU AND ITS OUTLIERS 555 

(i) the Superior Highlands of northern Wisconsin, northwestern Michigan, 
and northern Minnesota, and (2) the Adirondacks of northeastern New 
York, while it is practically continuous with the New England Plateau 
of related origin and character. Indeed the history of this great topo- 
graphic province is intimately associated with, and its forms are in 
many respects similar to, those of a considerable portion of the Appa- 
lachian region, and it is therefore necessary briefly to sketch its salient 
features. 

The Laurentian Plateau may be considered as a topographic unit, its 
chief features being those characteristic of a peneplaned region of 
crystalline rock — granites, gneisses, schists, etc. — bordered by over- 
lapping Paleozoic sedimentary layers which have been eroded into the 
form of an ancient belted coastal plain, then uplifted, extensively dis- 
sected by ordinary erosional processes in preglacial time, and, more re- 
cently, heavily glaciated. Two of the three great centers of glacial 
dispersion lay in the Laurentian province, the Keewatin and the Labra- 
dorian, and the effect of the great ice sheets that radiated therefrom was 
practically to denude the tract of its residual soils. With this set of 
physiographic conditions and changes we shall find associated practically 
all the topographic forms found in the region to-day.^ 

The dominating feature of the Laurentian region is the remarkably 
even sky line whose character is maintained in spite of the great diversity 
of rock structures and hardnesses which occurs from place to place. Al- 
most anywhere in the interior of the tract the horizon, as seen from an 
elevation, is almost as level as that of the sea and, also like that of the sea, 
is almost circular. The surface from point to point and in detail is 
decidedly broken, but in a general broad view it is strikingly flat and 
plateau-like. The degree of evenness may be appreciated from the fact 
that residual elevations of only 50 or 100 feet relative altitude stand 
out as prominent landmarks visible for many miles. The Laurentian 
area has been tiraversed by the officers of the Geological Survey of Canada 
in many different directions, and all the descriptions and photographs 
are alike in representing it as once having been one of the most typical 
peneplains in North America. Even in those parts of the now uplifted 
peneplain which have been most thoroughly dissected and glaciated, as 
in the region south of James Bay, the dominant topographic feature is 
still the even sky line intercepted only here and there by an occasional 

1 A. W. G. Wilson, The Laurentian Peneplain, Jour. Geol., vol. 11, 1903. 

The true character of the great Laurentian area of eastern Canada was first set forth by 
G. N. Dawson, then Director of the Geological Survey of Canada, at the Toronto meeting of 
the geological section of the British Association in 1897, and in 1893 a systematic description 
•of the region was prepared by Wilson. 



556 



FOREST PHYSIOGRAPHY 



isolated residual or monadnock which was able during the period of 
peneplanation to maintain a slightly greater elevation because of favor- 
able position on stream divides or superior hardness or both. The 
southeastern margin of the peneplain, where it borders the St. Lawrence 
River, is more rugged and uneven than the rest and is known as the 
Laurentide Mountains. Toward the extreme northeast and at the base 
of the Ungava peninsula there is a narrow range of mountains which 
extend to heights of 6000 to 8000 feet and stand prominently above 
the surface of the peneplain. The range includes the highest mountains 




Fig. 223. — The Laurentian Plateau as an uplifted, dissected, and glaciated peneplain in Labrador, 
east of Hudson Bay. Note the even sky line, the network of lakes, and the absence of a soil cover. 
(Low, Can. Geol. Surv.) 

in eastern North America. Broader and gentler undulations which give 
but slight diversity to the surface of the now uplifted peneplain also 
occur widely scattered in the form of low rounded domes and ridges 
roughly parallel to themselves and with their longer axes conforming in 
general to the strike of the rocks. ^ 

Differences in elevation between different portions of the peneplain are 
roughly indicated by the numerous lakes, large and small, which occur 
at levels but little below that of the general surface. From the eleva- 
tions of these lakes it is found that the average gradient of the valleys 
is from i to 4 feet per mile. East of Cree Lake as far as the junction 

' A. W. G. Wilson, The Laurentian Peneplain, Jour. Geol., vol. ii, 1903, p. 628. 



LAURENTIAN PLATEAU AND ITS OUTLIERS 557 

of Churchill and Little Churchill rivers the surface has an average 
gradient of 1.8 feet per mile for 450 miles; on the Hamilton River the 
gradient for about 300 miles, partly above and partly below the Grand 
Falls, has a mean value of approximately i foot per mile. Considering 
the large number of falls and rapids in the courses of the streams drain- 
ing the Laurentian Plateau these values appear astonishingly small, 
especially when compared with such gently sloping surfaces as those 
developed in piedmont areas. The average gradient of the plains of 
Alberta is from 2 to 3 feet per mile, a value which distinctly exceeds 
that of the ^general slope of the surface in the Laurentian province, 
although we are accustomed to thinking of the latter as rugged and the 
former as smooth. The Laurentian peneplain has been dissected to such 
an extent as to be rough but not rugged, though even its roughness is 
not expressed in the figures representing the gradient of the hilltop plane. 
Although the derivation of the great Laurentian area from a pene- 
plain is clear, it is worth while to see that it now exhibits but few of the 
characteristics of a peneplain. A peneplain is an old erosion surface of 
slight relief which has been worn down by normal physiographic agen- 
cies almost to the level of the sea. The typical peneplain is one which 
also bears upon its surface an occasional residual elevation, is mantled 
by deep residual soils, and is absolutely without lakes, falls, rapids, or 
any other features indicating a youthful condition of the drainage 
courses. It is noteworthy that scarcely any of these qualities are pres- 
ent in the Laurentian area to-day. Instead of residual soils there are 
here almost no soils at all, only locally developed patches of glacial till or 
of water-laid material glacially derived. Instead of well-organized and 
low-gradient drainage courses, the Laurentian area exhibits the most 
irregular drainage features and is, par excellence, the lake region of North 
America ; instead of standing near sea level the region is now at eleva- 
tions ranging from sea level to more than 2000 feet. Although it is 
one of the oldest portions of the continent, a large number of its fea- 
tures are due to a very recent geologic event — glaciation. In short, 
the Laurentian region is one which through unequal uplift and differ- 
ential stream and ice erosion has been so modified from its condition 
at the end of the preceding topographic cycle that its former peneplain 
character is recognizable only by the pronounced and uniform discord- 
ances that prevail throughout its entire area between general surface 
and geologic structure — a discordance that can be explained only by 
the assumption that it was once a region of prolonged erosion and that 
a pronounced, possibly a mountainous relief, was reduced practically to 
the level of the sea. 



558 FOREST PHYSIOGRAPHY 

REPRESENTATIVE DISTRICTS 

LAURENTIDE MOUNTAINS 

With these general features in mind we may now turn to the more 
detailed features of representative portions of the Laurentian area, 
beginning with the Laurentide Mountains that border the St. Lawrence 
Valley on the northwest. Perhaps the most important point in this 
district is that relating to the deformation which the Laurentian pene- 
plain suffered in the uplifting process that raised it to its present 
level. The uplift was differential and is still in progress; the general 
nature of the first uplift was a tilting of the whole northeastern corner 
of the continent upward at the north; the present movement is in har- 




Fig. 224. — The Laurentide Mountains north of St. Lawrence River at St. Anne de Beaupre. The lowland 
in the foreground is formed on limestone which terminates at the foot of the mountain slope. 

mony with and in continuation of the earlier movement. The Lauren- 
tide Mountains are due only in small part to their residual quality. 
They are due chiefly to the greater uplift of the peneplain along the 
border of the St. Lawrence Valley, so that its southeastern margin as 
viewed from the valley does not appear as the margin of a plateau but 
as a range of hills of sufficient height to be known as mountains. 
This marginal swell roughly parallel to the margin of the peneplain is 
succeeded toward the interior by a number of circular depressions oc- 
cupied by lakes, of which the St. John at the head of the Saguenay 
River is the most important. The streams of this portion of the 
plateau cross the marginal swell or the Laurentides through deep, steep- 
sided canyons of which the broadest and deepest is the fiord of the 
Saguenay. 



LAURENTIAN PLATEAU AND ITS OUTLIERS 559 



HUDSON BAY -ST. LAWRENCE DIVIDE 

From the Laurentide Mountains northwest to Hudson Bay the 
Laurentian area is a plateau formed upon ancient crystalline rock with 
an average elevation of about 1500 feet above sea level. It rises 
slowly from 1000 feet near the margin to about 2000 feet in the inte- 
rior. The surface is dotted with low rounded hills arranged in a series 
of ridges parallel to themselves and to the general strike of the rocks. 
These hills are the stubs of extensive and elevated mountain chains 
subjected tp prolonged erosion which brought them down to their 
present state.^ 

To the south of James Bay in the Nipissing and the Temiskaming 
regions the surface of the plateau consists of a succession of more or less 
parallel rock ridges with intervening valleys occupied by swamps and 
lakes and with a general elevation rarely falling outside the 900 to 1200 
foot limits. There are no very pronounced hills, the highest seldom 
attaining more than 300 feet above the adjacent country, while hills 
100 to 150 feet high are rather conspicuous topographic features. The 
areas of Laurentian granite and gneiss in the southern and southeastern 
portions of the district have weathered into a monotonous succession 
of hills and intervening rocky valleys; in the northwestern part of 
the Nipissing area there are more important elevations owing to the 
presence of resistant quartzite in country rock consisting of granite, 
diabase, and slate, the last-named member of the series weathering into 
a characteristically flat surface.- 

LABRADOR PENINSULA 

East of Hudson Bay is the Labrador peninsula, a rough tableland 
having an elevation of about 700 feet above sea level near its margin 
and about 2000 feet in its higher interior portions.^ The interior of the 
Labrador peninsula is so nearly flat that in an area of 200,000 square 
miles there is a difference in level of not more than 200 to 400 feet, and 
the highest general level of the interior is less than 2500 feet above the 
sea. The divides are often ill defined and never prominent. 

1 A. P. Low, The Mistassinni Region, The Ottawa Naturalist, vol. 4, 1890, pp. 11-28. 

2 A. E. Barlow, Report on the Geology and Natural Resources of the Area included between 
the Nipissing and Temiskaming. Map Sheet, comprising portions of the district of Nipissing 
and of the county of Pontiac, Can. Geol. Surv., vol. 10, n. s., Rept. I, 1899, p. 21. 

» A. P. Low, Report on Explorations in James Bay and the country east of Hudson Bay 
drained by Big, Great Whale, and Clear Water rivers. Can. Geol. Surv., vol. 3, n. s., pt. 2, 
Rept. J, 1888, p. 16. 



560 FOREST PHYSIOGRAPHY 

BARREN LANDS 

Likewise the "Barren Lands" in the far north of Keewatin, p. 565, 
although developed upon rock of most complex structure, are extraor- 
dinarily uniform in general elevation and in a broad view closely resemble 
the great plains of undulating grass-covered country of western Manitoba, 
Alberta, and Saskatchewan. Only here and there does a hard granite 
knoll projecting above the general surface indicate the character of the 
underlying rock and suggest the past history of the region. 

BORDER TOPOGRAPHY AND DRAINAGE 

Along the outer or southern and western border of the Laurentian 
peneplain is a group of land forms which represent on a great scale the 
general features of an ancient belted coastal plain. These features are 
best preserved in the region of the Great Lakes. The most continuous 
development of the cuesta feature is that associated with the outcrop 
of Niagara limestone which appears in the form of a pronounced but 
ragged escarpment extending from near Rochester on the southern 
shore of Lake Ontario diagonally northwestward through Ontario, form- 
ing the peninsula between Georgian Bay and Lake Huron. Thence it 
extends through Manitoulin Island and along the southern shore of the 
northern peninsula of Michigan. Farther west and southwest it con- 
stitutes the two peninsulas between Green Bay and Lake Michigan, and 
its final expression in the United States is in the southwestern corner of 
the Driftless Area, where it forms the boundary of an upland approxi- 
mately 100 feet above the general level of the country adjacent to it on 
the north.' 

West of Lake Winnipeg the Niagara escarpment again appears and 
fades out gradually to the north. Lakes Erie, Huron, Michigan, Mani- 
toba, and Winnipegosis are on the outer lowland of the ancient coastal 
plain; Lake Ontario, Georgian Bay, Green Bay, and Lake Winnipeg lie 
upon the inner lowland between the cuesta^ and the old-land;- Lake Supe- 
rior occupies a depression not associated with either lowland or cuesta. 

Upon the Hudson Bay side of the Laurentian Plateau a similar margin 
of Paleozoic sediments may be seen, although they are more extensively 
concealed by the deposits of the present coastal plain than is the case 

1 U. S. Grant, Lancaster Mineral Point Folio U. S. Geol. Surv. No. 145, 1909. See geo- 
logic map and descriptive text. 

2 The term cuesta is applied to the culminating ridge on the inner side of a dissected coastal 
plain. Its outer slope is long and gentle, its inner slope short and relatively steep. The term 
old-land is applied to any extensive tract of older and higher land that supplied land waste out 
of which the young land, or bordering coastal plain, was formed. 



LAURENTIAN PLATEAU AND ITS OUTLIERS 561 

on the southern margin. Over the peninsula southwest of Cape Henri- 
etta Maria in the angle between Hudson Bay and James Bay these 
Paleozoic sediments are developed to their greatest extent, but the 
cuesta feature is topographically very indistinct. On the eastern shore 
of Hudson Bay and James Bay the Paleozoic sediments have been 
dissected and submerged to the point where they now appear as chains 
of islands in some places continuous with anvil-shaped peninsulas. At 
one time the land stood higher than it now does, and dissection pro- 
gressed so far that with a later submergence of the region and the inva- 
sion of the eroded lowlands by the waters of Hudson Bay the cuesta 
was almost submerged; the degree of submergence was so great that 
the cuestas still appear as islands in spite of the great uplifts which the 
region has suffered in postglacial time. 

In a large number of instances the streams of the Laurentian 
Plateau discharge across its borders in gorges and canyons of note- 
worthy size and beauty. In places the gorges and valleys are steep- 
sided, narrow, and long; in other places they are short. They have their 
best development along the southeastern border, where the numerous 
streams that enter the Gulf of St. Lawrence from the northwest 
have deep canyons (sometimes with unscalable walls) cut to a depth 
of over 1000 feet below the general level of the plateau. A specific 
case is the Saguenay, through which Lake St. John discharges into the 
St. Lawrence. Lake Temiskaming and Ottawa River, as far down as 
Mattawa, likewise occupy long narrow depressions cut beneath the 
surface of the plain. All of these canyons and deep, steep-sided valleys 
are marked by topographic unconformities, that is, well-defined shoul- 
ders where the steep slope of the valley wall intersects the rather fiat 
slope of the upland surface, a clear indication that the canyon is of 
later origin than the upland surface below which it is incised. Where 
the deep preglacial canyons and gorges trend in the direction in which 
the ice flowed in the last glacial invasion the sides of the gorges have 
been steepened and the bottoms deepened. This is especially true of 
the Saguenay, which may probably be regarded as a typical glacial fiord, 
although it must be remembered that preglacial erosion had to a large 
extent prepared the valley for the maximum effects of glaciation as 
expressed in hanging valleys and deep channels below sea level. 

The fact that some of the long, narrow, and steep-sided gorges or de- 
pressions are at various angles with the direction of ice movement sug- 
gests that they owe their origin to the downfaulting of long narrow 
crust-blocks. This view would seem to be supported by the fact that 
Paleozoic sediments are preserved in the bottoms of many of the valleys. 



562 FOREST PHYSIOGRAPHY 

The sediments in the Lake Temiskaming and Lake Nipissing basins are 
in valleys lying below the level of the plateau. The margin is well 
defined, often cKffed, and the tributary streams spill over the edge of 
the basin in a series of waterfalls and cascades where they pass from 
the more resistant to the less resistant rock. 

The long narrow depressions may be explained also on the assumption 
of an early Paleozoic period of valley cutting followed by a period of 
valley filling. In this view later valley excavation would proceed along 
the outcrop of the relatively softer filling in the older valleys. It seems 
quite probable that further work will show the validity of both explana- 
tions each being applicable to a number of valleys to the exclusion of 
the other. 

SPECIAL FEATURES OF THE NIPIGON DISTRICT 

The topography of the Nipigon area north of Lake Superior is of 
special interest because the normal erosion features have been either 
partly masked or greatly complicated by lava flows. To the northeast 
of Lake Nipigon is the Archaean old-land of crystalline rock containing 
numerous outliers of sedimentary strata. The southwestern portion of 
the present basin of Lake Nipigon represents a maturely dissected por- 
tion of the inner lowland of the ancient coastal plain. 

At a time when the relief of the coastal plain was at a maximum 
there occurred extensive intrusions of diabase and extrusive flows of 
basalt which to a large degree filled the inner lowland and even in some 
places poured out over the adjacent uplands. This period of lava 
flows followed the erosion that in turn followed peneplanation. Since 
its formation the diabase has been very extensively eroded so that only 
from 5% to 10% of it remains, but its occurrence dominates the 
region to such an extent that practically every prominent feature of 
the topography for one hundred miles along the southwest shore of 
Lake Nipigon and the adjacent country is associated with the trap 
sheets. Their upper surface is usually a tableland or mesa, and gorges 
have been cut to a large extent through the sheets by the draining 
streams. Beneath the basalt may be seen from place to place portions 
of the old peneplain which were still in existence when the flows occurred 
and which were covered over and so preserved by the resistant rock. 
The scenery is varied, bold, and picturesque, as determined by the 
sharp outlines of the igneous rocks whose cliffs were still further cleaned 
and freshened by glacial action. 



LAURENTIAN PLATEAU AND ITS OUTLIERS 563 

CHANGES OF LEVEL 

The change of level which the Laurentian Plateau is now undergoing 
and which it has undergone in postglacial time is shown in a variety 
of most convincing ways. At Cape Nachvak, one hundred and forty 
miles south of Hudson Straits, are old strand lines reaching up to 1 500 
feet above sea level. Also on the east coast of Hudson Bay are well- 
preserved and numerous terraces cut in till and other deposits reaching 
to an elevation of 300 feet above the sea. Deep-water species of shells 
are washed out of the present beach and are found in stratified clays 
up to elevations of 500 feet; and long, continuous lines of driftwood, 
chiefly spruce and cedar, occur 30 feet above tide. These data combine 
to prove that the region has suffered important changes of level so 
recently as still to preserve in the clearest manner the features indicat- 
ing uplift. Besides the physical features there are a number of impor- 
tant and convincing pieces of human evidence. The Eskimos of the 
region catch fish by constructing weirs of stone which at low tide 
impound fish that have come up close inshore during high tide for feed- 
ing purposes. These fish weirs and traps are found at all elevations up 
to 70 feet above present sea level, and as their use is invariably asso- 
ciated with the shore line of the time when they are employed, it is 
clear that the level of the land has changed not less than 70 feet 
since the Eskimos have inhabited the region. Hudson mentions win- 
tering in a bay full of islands where now only a canoe may pass, and 
the salt marshes about the border of Hudson Bay are drying up to such 
an extent that the geese and ducks which formerly made their home 
among them have extensively abandoned them, and the residents of the 
district find it increasingly difficult to secure the eggs of these wild 
fowl. Finally, the Indians often remark the growing distances between 
old buildings, forts, trees, and the shore line, although this piece of evi- 
dence is of course far less convincing than the others.^ 

On the east coast of Labrador along the iioo miles from St. John to 
Cape Chidley no careful measurements of postglacial uplift have been 
made, although Daly has approximated the amount by observations 
upon the distribution of bowlder clay and bowlders. ^ He concludes 
that the higher bowlder-covered zone has never been submerged since 
the ice sheet retreated from the country, and that the lower bowlderless 
zone is a wave-swept zone. He finds that the smooth unbroken surfaces 

1 R. M. Bell, Proofs of the Rising of the Land around Hudson Bay, Am. Jour. Sci., vol. i, 
4th ser., 1896, pp. 219-228. 

' R. A. Daly, The Geology of the Northeast Coast of Labrador, Bull. Mus. Comp. Zobl., 
vol. 38, 1902, p. 254. 



564 FOREST PHYSIOGRAPHY 

of the roche moutonnees in the bowlder-covered zone (about 75 feet 
above sea level) contrast strongly with the jagged and riven wave-swept 
ledges below that level. Low, steep, and rugged cliffs are sometimes 
found associated with pebble and bowlder beaches of Hmited develop- 
ment. The elevatory movements continue in both Labrador and New- 
foundland, as determined by the testimony of the inhabitants in regard 
to the decreasing depth of water on the beach and the gradual shoaling 
of water over ledges and bowlders off shore. The recency of the shore 
uplift is also shown in the numerous fresh- water ponds lying back of the 
barrier beaches — ponds that at one time were true coastal lagoons on 
the landward side of submarine bars. The forms are strikingly fresh, 
the glaciated, bordering slopes having contributed but little land waste 
to shore filling. 

THE LAKE REGION 

The Laurentian area of Canada constitutes the greater part of the 
lake region of North America whose boundaries are shown on p. 565. 
It has been stated that there are areas within it 25% of whose surface 
is occupied by lakes.^ In order to get a closer value for this interesting 
condition the actual areas of the lakes represented upon a detailed map 
by Collins,^ Fig. 225, were carefully measured. Some thirty independent 
measurements of the lake areas afford a mean that is close to accuracy. 
The result: about 16% of the total area of the district is covered ^vvith 
water. When it is considered that this value is for a representative dis- 
trict the figure is very striking indeed. However, even on this map 
only the more prominent lakes were represented on the original sheets. 
Were even the smallest lakes included, at least 20%, and possibly 25%, 
of the surface would be found covered with water. To secure a com- 
parable figure for total lengths of drainage systems composed of lake, 
about 2000 miles of river course were measured, with the result that the 
rivers examined showed lake in 57% of their total length. 

To a large extent the abundance of lakes in the prevailingly rocky 
Laurentian Plateau is due not alone to glaciation but to glaciation of a 
peneplain of such perfect development that the slightest degree of rough- 
ening by differential erosion would produce enclosed basins in large 
numbers. If the region were mountainous the effect of glacial erosion 
would be in the main to deepen the valleys and basins already formed 
and accentuate the preglacial differences of level and topographic form. 
We have only to recall the appearance of the glaciated mountain region of 

1 A. W. G. Wilson, The Laurentian Peneplain, Jour, of GeoL, vol. ii, 1903, pp. 645-650. 

2 W. H. Collins, Report on a Portion of Northwestern Ontario traversed by the National 
Transcontinental Railway between Lake Nipigon and Sturgeon Lake, Ann. Rept. Can. Geol. 
Surv., 1908. 



LAURENTIAN PLATEAU AND ITS OUTLIERS 



565 




566 



FOREST PHYSIOGRAPHY 



the northern Cascades and the northern Rockies, with their strong topo- 
graphic discordances, to appreciate how different the Laurentian area 
would appear if its local reUef had not been so slight as to be almost 
negligible. Even rocks of the same geologic age and general character 
vary sufficiently from place to place to cause important differences in 




Fig. 226. — Details of drainage in a limited portion of the Laurentian Plateau. (Based on Can. Geol. 
Surv. Maps and Railway Surveys by Collins. ) 

topography; and when it is considered that so large a variety of rocks 
as granites, gneisses, schists, slates, and trap sheets that occur here extend 
these differences in resistance from place to place, it is clear that some 
roughening of the old peneplain must follow upon erosion of any sort and 
that in the case of ice the roughening would result in the formation of 
a very large number of lake basins. The preglacial slopes were almost 
never so strong as to overcome the general irregular scooping action of 
the ice, and every local overdeepening either as the result of decreased 
rock resistance or of glacial convergence produced reversed slopes that 
were occupied by lakes as soon as the glacial cover withdrew. 



LAURENTIAN PLATEAU AND ITS OUTLIERS 567 

It is clear that the glaciation of the Laurentian Plateau would result 
in the formation of a large number of lakes, and that the lakes would be 
extremely irregular in contrast to the regularity of the lakes that occupy 
overdeepened portions of glaciated mountain valleys. Labyrinthine 
shores and shapeless islands are the rule in the Laurentian of Canada. 
The maze of waterways displayed by this region is the marvel of every 
traveler in it. 

The readiness with which some of the lake basins were formed may be judged from the fact 
that but a sHght change of level may effect a change of outlet, as has been suggested many times 
in connection with the two-outlet phenomena commonly displayed by many of the Laurentian 
lakes. The feature was regarded as a novel one when first described, but the repeated finding 
of lakes with two outlets shows it to be a very much more general occurrence than was at first 
supposed. It has already been noted that the whole northeastern corner of the continent is 
suffering a change of level and that the movement is upward on the north. The result, in the 
case of lakes lying in depressions with low rims, is to cause a new outlet to come into existence 
as the old outlet ceases to function through uplift. The abandonment of an old outlet would of 
course be gradual and for a time two outlets would function. Even without such a change of level 
it has been thought that two-outlet lakes may have been caused by the formation of excep- 
tionally shallow basins on a peneplain surface. The two-outlet feature is indeed thought to be 
on such a scale as to be independent evidence of the tilting of the land. In some cases, how- 
ever, where two and even three outlets are in existence, they are found on the same side of a 
lake. Lake Chibougamou (50 miles south of Lake Mistassini), for example, is drained by two 
outlets both of which are on the east side.i In such cases the two-outlet feature is unrelated to 
regional tilting and appears to be due instead to coincidence in the level of low cols on the rim of 
the lake basin. The condition is perpetuated by the hard rock which is but little affected by 
the clear streams. 

Besides the island-dotted lakes with ragged shores there is a distinct 
though comparatively small class of lakes that has more regular features. 
These lakes are usually longitudinal and are caused in a number of 
different ways. In some cases they owe their existence to the erosion of 
soft dikes, as, for example, the peninsulated northern shore of Lake Supe- 
rior with its long narrow bays and points. The dikes are commonly of 
greenstone, though sometimes they are of pegmatite, and in both cases 
are usually soft and their outcrop covered with lakes or streams. Some- 
times the correspondence of position of former dike and later river 
or lake is so close that where the dike narrowed the lake or river 
was narrowed and where it widened the drainage features widen. It 
must not be forgotten, however, that the dike material is not always 
softer than the country rock ; where it is harder it stands out as a promi- 
nent ridge instead of a lake basin or a river valley. -The straightness 
of trend of the dikes within short distances is directly related to the 
straight-line topography and drainage so characteristic in many portions 
of the area as to give a pronounced appearance of artificiaUty to it. 
Lake Temiskaming and the "Deep River" of the Ottawa drainage sys- 
i Data from Bateman, Can. Geol. Surv. 



568 FOREST PHYSIOGRAPHY 

tem are examples of longitudinal lakes, but their origin may have been 
due to crustal warping or to block-faulting of the graben type. In still 
other cases the longitudinal lakes are due to blocking of valleys by glacial 
material. 

In addition to the lake types of the Laurentian that we have noted 
there is another class dependent upon broader and less local conditions. 
These lakes lie on the border of the region and their occurrence is coin- 
cident with that of large isolated areas of sedimentary rock within or 
on the border of the crystalline area. Whether these sedimentary 
masses represent downfaulted blocks of rock formerly more extensive 




Fig. 227. — View on the shore of Lake St. John, Quebec. The level sky line in the background represents 
the Laurentian Plateau; in the foreground is a lowland developed on limestone; in the middle distance 
are alluvial terraces. 

than now, and preserved by downfaulting because carried below the gen- 
eral level of the peneplain surface, is not certainly known, but the 
explanation has a high degree of plausibility, for faulted zones have 
been found about the borders of some of them and everywhere the 
sediments are sharply localized and extend to great depths below the 
level of the ancient peneplain. Whatever their origin they were 
areas of weakness during the glacial period and indeed ever since 
the elevation of the peneplain, with the result that not only do lake 
basins lie in them but the outcrop of the softer sedimentaries is always 
marked by the existence of a lowland whose border is sharply de- 
termined by the crystalline rocks that rim about it. A typical occur- 
rence is at Lake St. John, which occupies a portion of an outlier of 
the Paleozoic sediments that border the St. Lawrence Valley on the 
north. The outlet of Lake St. John is over a harder rock rim to the 



LAURENTIAN PLATEAU AND ITS OUTLIERS 569 

Saguenay, and falls and rapids mark the transition from one rock belt 
to the other. Hamilton Inlet, Great Bear and Great Slave lakes, and 
many other depressions have a similar origin, and in all cases small por- 
tions of the older sedimentary rock still cling to the border of the de- 
pressions in the crystalline tract, or, as at Lake St. John, occur in larger 
masses forming lowlands. 

Lakes are known to be ephemeral features of the earth's surface 
and to be the easy prey of geologic processes. Commonly the streams 
that feed lakes b,ear such quantities of material into them and the drain- 
ing streams cut down the rim at the outlet so fast and vegetation ac- 
cumulates so rapidly that the life of a lake is in a geologic sense short. 
It is therefore interesting to find in this great lake region developed on 
the Laurentian of Canada a set of conditions that insure the longevity 
of the lakes within it, so that at least a whole geologic period would 
seem to be a conservative estimate of the length of time these lakes will 
persist. The principal conditions that are the basis for this conclusion 
are as follows. The fresh-rock rims have an exceptionally high degree 
of resistance. Instead of rotten rock the rock enclosing these lakes 
is firm. The products of decay were swept off by the continental ice 
sheet, leaving the undecomposed rock of the subsurface. Although falls 
and rapids abound the average gradient of the draining streams is only 
one to two feet per mile. In addition to the practical absence of land 
waste over vast portions of the Laurentian area, lakes are so abundant 
that the water is thoroughly filtered and the sediments are thoroughly 
entrapped. The streams are thus deprived of their cutting tools and 
waterfalls and rapids retreat with amazing slowness in the extremely hard 
rock. More powerful than these factors in extinguishing some of the 
Laurentian lakes is the vegetation that grows in such abundance about 
the borders of the shallower lakes as sometimes quickly to effect their 
reclamation. Lakes are turned into swamp or muskeg and then finally 
reclaimed, but the process is largely limited to the smaller and shallower 
lakes and does not affect to an important degree the conclusions we 
have just stated concerning the life of the lakes as a group. 

VEGETATION 

There is a limited forest growth in the hollows and along the borders 
of the Labrador region, but large portions of the interior are barren 
tracts of rock and muskeg. Exceptionally good forest tracts are found 
in a number of places. On the 51st parallel and east of Lake Mistassini, 
whence the Porcupine Range extends toward the north, is a well-wooded 
tract. The black spruce is here the predominating species. Other trees 



570 FOREST PHYSIOGRAPHY 

are the white birch, poplar, willow, alder, and Banksian pine. The growth 
is surprisingly large; the diameters of the largest trees exceed 2 feet and 
the height attains 70 or 80 feet.^ Quebec and Ontario south of James 
Bay are densely forested, the forests extending westward to wi-thin a short 
distance of Great Slave Lake. Beyond this point the region may be 
described as a treeless moss-covered tundra whose subsoil is perpetually 
frozen. The northern boundary of the great transcontinental spruce 
forest closely follows the western shore of Hudson Bay from the mouth 
of Churchill River for a few miles, then curves gently inland; thence it 
extends northwesterly, crossing Island Lake, Ennadai Lake on Kazan 
River, and Boyd Lake on the Dubawnt. The next dividing point is just 
north of 60° on Artillery Lake. From this point the line curves south- 
westerly, crossing Lake Mackay south of latitude 64°. The banks of 
the Coppermine are the boundary to 67°. Tongues of timber follow 
the northward-flowing streams, with their warmer water, well into the 
Barren Grounds. The most remarkable stream of this kind is the 
Ark-i-linik, a tributary of Hudson Bay. From a point near latitude 62!° 
north, within the main area of the Barren Grounds, a more or less con- 
tinuous belt of spruce borders the river to latitude 64!°, a distance of 
over 200 miles by river. A few species of woodland-breeding birds 
follow these extensions of the forest to their limits. Alders occur in 
more or less dwarfed condition in favorable places well within the treeless 
areas, and several species of willows, some of which here attain a height 
of 5 or 6 feet, border some of the streams as far north as WoUaston Land. 
These are the only trees which occur even in a dwarfed state in the Barren 
Grounds proper. 

The principal trees of the spruce forest, whose northern limit is thus 
defined, are the white and black spruce, whose range is coextensive 
with the forest limits, the canoe birch, tamarack, aspen and balsam 
poplars, Banksian pine and balsam fir common in the southern part of 
the belt and terminating from south to north about in the order given. 
With these are associated, generally in the form of undergrowth, a 
number of shrubs. The tree limit on the western mountains in lati- 
tude 56° is about 4000 feet. The head of the Mackenzie delta is 
marked by islands well wooded with spruce and balsam poplar. Lower 
down these trees give way to willows, which continue to the Arctic 
shore.2 

South of the line noted above is a belt of conifers stretching across 

1 R. McFarland, Beyond the Height -of -Land, Bull. Phil. Geog. Soc, vol. 9, 1911, p. 31. 

2 E. A. Preble, A Biological Investigation of the Athabaska-Mackenzie Region, North 
American Fauna, Bureau of Biol. Surv. No. 27, iqo8. 



LAURENTIAN PLATEAU AND ITS OUTLIERS 



571 



northern North America from Hamilton Inlet to Great Slave Lake, 
the trees increasing in size and variety toward the south. This is the 
great spruce forest belt of Canada, whose characteristic growths are 




Fig. 228. — Map showing distribution of the dominant conifers in Canada and eastern United States. 

(Transeau.) 



spruce, fir, poplar, willow, alder, tamarack, etc., and in the Great 

Lake region its borders are covered with forests of deciduous hardwood.^ 

The uniformity of level, the prevailing absence of soils, and the 

widespread occurrence of lakes, favor uniform life conditions through- 



1 R. M. Bell, The Geographical Distribution of Forest Trees in Canada, Scottish Geog. 
Mag., vol. 13, 1897, pp. 281-296. 



572 



FOREST PHYSIOGRAPHY 



out the region, a fact well shown by the widespread distribution of the 
fur industry, which is also favored by the equally widespread forest 
growth, while the network of navigable streams and lakes makes com- 
munication relatively easy as unsettled countries go. 

Superior Highlands 

After consideration of the topographic, drainage, and soil conditions 
of the Laurentian area of Canada the features of the Superior High- 
lands may be easily appreciated, for this physiographic province is but 
a part, strictly speaking, of the great Laurentian area of Canada. Like 
the latter, its sky line is distinctly even and gives little hint of the moun- 







Fig. 229. — Typical drainage irregularities in the Lake Superior Highlands. 
(U. S. Geol. Surv.) 



tainous structures that prevail almost everywhere within it. Its prin- 
cipal topographic feature is an uplifted and dissected plain of erosion 
which has been glaciated and hence has many secondary features due 
to ice erosion. It lies neither in the region of pronounced glacial aggra- 
dation nor in that of intense glacial denudation; hence those forms that 
are of glacial origin are due in some cases to ice scour, in others to ice 
accumulation. A certain amount of glacial detritus occurs here and 
there; in other localities the surface is swept practically clean by gla- 



LAURENTIAN PLATEAU AND ITS OUTLIERS 



573 



cial erosion. The glacial material is irregularly disposed in character- 
istic fashion and blocks the drainage to such an extent that lakes and 
ponds occur in large numbers. The most common type of depression 




Fig. 230. — The heavy broken line is the boundary between the Superior Highlands on the north and the 
Prairie Plains on the south. It is, however, more prominent as a geologic boundary than as a topo- 
graphic boundary. Note the connection at the western end of Lake Superior between the Superior 
Highlands and the Laurentian Plateau of Canada. The special districts indicated are portions of 
the region described in the text. 



is in the form of a small basin partly grown up to bushes and grasses, a 
swampy tract called a "muskeg." 

In describing the detailed features of the area we shall select three 
tracts that have been well explored and that are representative of the 
whole area. In examining them it is well to remember a number of 
general features. The region consists of crystalline rock, — gneiss, 
granite, and schist as well as slate, dolomite, sandstone, limestone, and 
other types. The crystalline rock predominates throughout the greater 
part of the area; the sedimentary rock occurs chiefly upon the borders. 
The crystalline rock dips at so high an angle that it is often vertical, 
thus exposing rock types of different hardnesses side by side in narrow 
belts. The result is that a valley carved in the soft rock may not be 
very deep and yet may have nearly vertical sides, so that the country 



574 FOREST PHYSIOGRAPHY 

often has a very rugged appearance in detail that is the result of recent 
erosion and yet not lose on the interstream areas that plateau quality 
that is the result of prolonged erosion in early (pre-Cambrian) and later 
(Jurassic-Cretaceous) geologic time. The structure of the sedimentary 
rocks (Paleozoic) is in sharp contrast to that of the crystallines. The 
former lie in comparatively flat attitudes, dipping only slightly out- 
ward (southward), Fig. 232. In many places outliers of these flat to 
gently inclined strata occur beyond the main border of the sedimen- 
taries and in such instances cap the vertical crystallines and accentuate 
the plateau quality of the region. Their nearly vertical cliffed borders 
add also to the steepness of the valley sides. - 

Almost the entire zone of decomposed rocks formed in preglacial 
time in the Superior Highlands was removed by glacial erosion; in- 
deed glacial truncation was so pronounced as seriously to reduce the 
amount of available iron ore in the Lake Superior region. In many 
places the ice cut deeper into the soft ore bodies than into the adjacent 
harder rocks and thus produced subordinate valleys in sympathy with 
the ore deposits, a feature that is well illustrated in the Mesabi district. 
The soft ores were so comminuted that they are not easily distinguish- 
able in the drift, but the hard ores occur in the glacial drift farther 
southeast and indeed in the whole region so plentifully that it is clear 
that a great portion was swept away by the ice.^ 

REPRESENTATIVE DISTRICTS 
CRYSTAL FALLS DISTRICT ^ 

The Crystal Falls district in the Superior Highlands is a somewhat 
rolling plain sloping gently downward to the southeast at an average 
rate of a little less than 20 feet per mile. Its average elevation is 
1200 to 1300 feet above the sea. This plain is formed in part upon soft 
and gently inclined sandstones (Upper Cambrian) and in part upon 
crystalline and much harder and more highly tilted rocks (pre-Cam- 
brian) of varying characters, though it everywhere maintains a very 
uniform slope regardless of the underlying rock formations. The minor 
topographic features of the plain have a large variety of form and 
detail yet very small relief. There are no commanding eminences and 
the sky line is generally even. Portions of the border of the mountain 

1 C. R. Van Hise, The Iron Ore Deposits of the Lake Superior Region, 21st Ann. Rept. 
U. S. Geol. Surv., iSgg-igoo, pt. 3, pp. 333-3S(>. 

2 H. L. Smythe, The Crystal Falls Iron-bearing District of Michigan, Mon. U. S. Geol. 
Surv. No. 36, 1899, pp. 331-333. 



LAURENTIAN PLATEAU AND ITS OUTLIERS 



la.are composed of crystalline rock, and here the sur- 
e is dotted with rocky knobs generally elongated east 
Id west, which is the direction both of the gneissic folia- 
fn and of the ice movement. The elevations rise 5, lo, 
, and in some cases 60 feet above the intervening de- 
ssions and have steep smooth walls. The slight relief 
the district is indicated by the fact that the more 
ominent elevations are deposits of modified drift. Only 
casionally are they due to small rock masses of harder 
iterial, as Michigamme Mountain, which reaches an 
jvation of 200 to 300 feet above the general level, an 
jivation sufficiently great in a region of very slight relief 
I result in the application of the name "mountain" to 
lat would generally be regarded as a very insignificant 
pographic feature. The details of the topography are 
jimarily glacial in origin and only secondarily a response 
[ geologic structure. 

[The almost innumerable muskegs or basin-like depres- 
bns are the work of either irregular glacial cutting or 
ling. Where softer rock occurs the ice gouged out a 
ipression; where the rock is exceptionally resistant a 
{hob or ridge is the result. Hills of glacial drift are 
j:attered about the surface in large numbers. A glacial 
!)il is also developed over a large part of the tract but 
ijas been entirely washed away and the rock surface laid 
'ire on many steep slopes where it was originally thick 
ad where fires and lumbering operations have removed 
jie forest cover and allowed soil erosion to take place. 
fhe structural domes of crystalline rock have a character- 
tic topographic expression, their margins being fre- 
Ijuently abrupt and in places marked for considerable 
istances by scarp-like slopes in the granites where ver- 
f.cal contacts with softer formations occur. These broad 
ones of harder rock are separated by broad and slightly 
)wer lying plains, in many of which a valley character 
; still distinguishable in spite of extensive glacial modi- 
ication. The existing drainage follows in a general way 
lie older (preglacial) valleys, although the relation is 
oftentimes much confused in its details since glacial drift 
jow lies irregularly disposed on the floors of the pre- 
lacial valleys. 



575 



■5 Vi 



S t5 



fLI >i- 









(J 4) 




.a s 

a o 






;76 



FOREST PHYSIOGRAPHY 



M" 



■r 







LAURENTIAN PLATEAU AND ITS OUTLIERS 



577 



SOUTHERN DISTRICT 

The southern portion of the Superior 
Highlands (central-northern Wisconsin) con- 
sists of a main upland, an uplifted and dis- 
sected peneplain with a very even summit 
below which the Wisconsin River and its 
tributaries have eroded their valleys and 
above which project a few isolated hills and 
ridges. The plain gradually descends south- 
ward and finally diverges; one plane runs 
under the Potsdam sandstone which forms 
the northward margin of the Paleozoic de- 
posits of the region and another extends 
across the Paleozoic formations. In the 
vicinity of Grand Rapids, Wisconsin, and 
approximately at the border of the sand- 
stone district, looo feet above the sea, the 
valley bottom of the Wisconsin River prac- 
tically coincides with the level of the lower 
or pre-Cambrian plain. The pre-Cambrian 
and the main crystalline rocks are very 
much folded and crumpled and the dips are 
at various angles and frequently almost ver- 
tical, Fig. 233.^ 

The structures are such as are associated, 
in the early stages of a first topographic 
cycle, with topographic features of moun- 
tainous proportions and in their present 
planed condition indicate that widespread 
peneplanation has taken place. The strati- 
graphic conditions show that this peneplain 
was of pre-Cambrian age and was buried by 
Paleozoic sediments to be reexposed by the 
long interval of erosion between the Creta- 
ceous and the Quaternary. During the 
Jurassic-Cretaceous cycle of erosion the mar- 
ginal deposits were in part stripped from 
the pre-Cambrian peneplain and in part 

1 S. Weidman, The Geology of North-Central Wiscon- 
sin, Bull. Wise. Geol. and Hist. Surv. No. 16, igoy, pp. 
592 ff. 



%r 






=^^^0. 






'">'D( 



578 FOREST PHYSIOGRAPHY 

beveled to the form of a lowland plain. The Cretaceous peneplain 
made but a slight angle with the pre-Cambrian peneplain, and the 
widespread occurrence of the later peneplain in this region is probably 
to be ascribed in large part to the earlier peneplanation which had 
largely obliterated the relief. 

Adirondack Mountains 

The Adirondacks are a small group of mountains in northeastern 
New York whose northern and southern slopes descend to tidal valleys, 
the Hudson and the St. Lawrence. The relative altitudes are therefore 
great and the absolute altitudes are such that the dominating peaks rank 
with the highest in the eastern half of North America. Mt. Marcy (the 
"Tahawus" or "Cloud- Splitter" of the Indians) rises to 5344 feet above 
the sea, and Whiteface is not much lower with an altitude of 4900 feet. 
For a long time after the fertile and easily traversed valley of central 
New York had been inhabited the Adirondacks were still an untamed 
wilderness. Dense forests clothed slopes and summits alike; deep valleys 
with steep descents and tillable land of small extent did not tempt the 
farmer. 

GEOLOGIC STRUCTURE 

The whole of the Adirondack region consists of a great series of 
metamorphic rocks, — sediments, gneisses, quartzites, and coarsely crys- 
talline limestones on the one hand and igneous rocks, such as syenites, 
granites, and gabbros on the other. Roughly speaking, the region is 
composed essentially of gneiss, with numerous and rather generally 
scattered limestone belts, the whole cut through on the east by immense 
intrusions of gabbro. The rocks and their relations are very similar to 
those of the Laurentian area of Canada. Excepting the limestones all 
of the rocks are hard and resistant to erosion, so that their weak points 
are structural features — to a small degree their planes of schistosity and 
to a greater degree their joints and faults. Wrapping all about the Adi- 
rondack nucleus are sedimentary strata, chiefly of marine origin, whose 
material was largely derived (in so far as it is land-derived) from the 
Adirondack massif during the prolonged periods of erosion in which the 
Adirondacks existed as land masses. In some cases, as on the west and 
northwest, the sedimentary rocks (Paleozoic) overlap the crystalline 
rocks (pre-Cambrian) of the mountain mass; in other cases, as on the 
northeast and east, the transition from the rocks of the mountains to 
those of the bordering plateaus and plains is more abrupt — the result 
of block-faulting somewhat modified in detail through the influence of 



LAURENTIAN PLATEAU AND ITS OUTLIERS 579 

post-faulting erosion and glacial action. In general the sedimentary 
rocks — sandstones, limestones, and shales — have little to do with the 
physiography of the mountains, for with few exceptions they lie on their 
border. 

TOPOGRAPHY AND DRAINAGE 

A striking feature of Adirondack relief is the strong contrast between 
the eastern and western halves of the mountain tract. The western half 
of the Adirondack area is really an extensive upland; the eastern half 
alone is truly' mountainous. Broad and moderately deep valleys are 
characteristic of the western area, and the accordance of summits makes 
the plateau feature. almost as prominent as in the Appalachian Plateaus 
and decidedly more so than in the Catskill Mountains. The prevail- 
ing flatness is diversified solely by the broad valleys and certain low 
hills which are probably residuals upon the Cretaceous peneplain whose 
level the even upland seems to represent. The eastern area was never 
base-leveled, or, if so, all traces of a former erosion surface appear to 
be lost in the changes that have since occurred. That the area should 
have escaped base-leveling is so remarkable, considering the perfection 
of development of the base-leveled surface in other localities around it, 
that a great deal of attention has been paid by geographers to this fact. 
Burial and reelevation have been suggested, with the inference that, 
during burial, erosion ceased here while it continued elsewhere; later 
erosion, the stripping off of the sedimentary cover, and the reexposure 
of a once buried peneplain or old surface are other assumptions re- 
quired by this suggestion. Perhaps the most plausible suggestion is 
that the Adirondacks represent the locus of repeated movement 
and that the forces of erosion and uplift have been nearly balanced, so 
that while erosion has been tending toward the production of a base- 
leveled surface this tendency has been effectively offset by repeated 
uplift. It is known that the Adirondacks have been free from extensive 
folding since early geologic time (Ordovician), though they have prob- 
ably been subjected to broad uplift, for sediments younger than the 
Ordovician have been uplifted by considerable amounts and the moun- 
tains have been uplifted by equal and possibly greater amounts. 

The rugged eastern half of the Adirondacks is composed of mountains 
that have certain very striking features. Mounts Marcy and White- 
face, the two principal mountains of the Adirondack tract, are composed 
of granite and stand well above the general level. The central cluster 
of high peaks to which they belong is surrounded by a plateau-like 
tract interrupted by valleys with rather gentle slopes developed upon 
softer beds and now largely drift-filled. The granites are, however, 



58o 



FOREST PHYSIOGRAPHY 



not abrupt in form; they have a gentle, rather flowing outUne, due to 
the fact that denudation has passed the stage of greatest activity. 
Though the Adirondacks were not obliterated during the long erosion 
cycles in which the surrounding tracts were peneplaned they were greatly 
reduced in height and softened in form. Those valleys that were de- 
veloped upon the softer rocks were broadened and reduced to base level, 
while even those valleys that were developed in the crystallines acquired 




Fig. 234. — The plateau-like western portion of the Adirondack Mountains in contrast to the 
mountainous eastern portion. Contour Interval, 500 feet. 



moderate slopes .^ This marked roundness of the Adirondack mountain 
forms has no doubt been slightly increased by the action of the continental 
ice sheet which overrode the highest peaks of the mountains, although 
the glacial effects should be regarded rather as finishing touches than as 
important modifications.^ 

1 I. H. Ogilvie, Glacial Phenomena in the Adirondacks and Champlain Valley, Jour. Geol., 
vol. 10, 1902, p. 410. 

2 R. S. Tarr, Physical Geography of New York State, 1902, pp. 46-47. 



LAURENTIAN PLATEAU AND ITS OUTLIERS 581 

The main outlines of the eastern Adirondacks were determined by 
faulting, while the detailed features are due to minor structural con- 
ditions such as fissures, joints, etc. The eastern section of the moun- 
tains, as shown in Fig. 234, is most affected by faults which have 
given the topography much sharper outlines than are as a rule found 
elsewhere in the Adirondacks. The faults trend northeast-southwest 
and northwest-southeast in two major fault systems and north and south 
in a third system of lesser importance. These faults control the trends of 
both the mountains and the intervening valleys and give them their 
most distinctive character. The mountain profiles are typically ser- 
rate, with a gradual slope on one side cut off by a steep slope on the 
other. The slopes that look to the southeast or northwest are particu- 
larly steep if not precipitous, with less pronounced steep slopes at right 
angles to them. So deep are some of the intermontane valleys and 
so steep their margins, it has been suggested that they look like un- 
drowned fiords. Lower Ausable Lake and the central part of Lake 
George are illustrations of valleys which occupy depressed blocks or 
grahen between the relatively elevated crust blocks that constitute the 
mountains. The valley trends are curiously related in the case of both 
tributaries and master streams and even in different sections of a single 
valley. There is generally a pronounced angularity or trellis pattern to 
the drainage, which is commonly associated with mountains of the Appa- 
lachian type that have been base-leveled and rejuvenated. In the Adi- 
rondacks, however, the pattern is unrelated to rock belts; it is due entirely 
to block-faulting, and had the pattern of the faulting been more irregular 
the drainage courses would now be more irregular. 

The faults of the crystalline portion of the Adirondacks can not be worked out either in 
detail or with much accuracy, but on the borders of the mountains where sediments overlap 
the crystallines a means for determining the amount of faulting is supplied. One such fault 
in which the surface of a down-thrown block forms the bottom of a topographic depression or 
trough occurs near Northampton. The bordering parallel faults run north-northeast and have 
well-defined abrupt scarps about 6 or 7 miles apart. They involve up to 1500 feet of struc- 
tural displacement, and the topographic depression thus created is about 1000 feet deep.' The 
occurrence is of particular interest because it is so clear-cut as to strengthen the previous ex- 
planations of the fault origin of scarps and troughs of similar character in adjacent tracts where 
a stratigraphic means for the determination of the amount of faulting is not at hand .2 

On the western shores of Lake Champlain and on the shores of many 
other larger lakes of the Adirondacks, block-faulting has given a charac- 
teristic outline to the coastal topography. Sharp headlands with definite 

1 See the Broadalbin quadrangle, U. S. Geol. Surv. 

' W. J. Miller, Trough Faulting in the Southern Adirondacks, Science, n. s., vol. 32, 1910, 
pp. 95-96. 



582 



FOREST PHYSIOGRAPHY 



trend project from the general course of the coast and in many cases form 
the extensions of block-faulted mountains whose intervening valleys, 
formed on the downthrown blocks, are submerged. In general the faults 




Scale of 3Iiles 



Contour interval 100 feet 



Fig. 235. — Rectangular pattern of relief and drainage lines in fault-block mountains of the eastern Adiron- 
dacks. (Part of Elizabethtown quadrangle, U. S. Geol. Surv.) 



are compound, giving a terraced quality to the mountain slopes. On 
the slopes bordering Lake George the trees grow in pronounced rows 
or bands on these structural terraces, with thinner lines or bands between 
where the steeper slopes, thinly covered with soil, supply but little avail- 



LAURENTIAN PLATEAU AND ITS OUTLIERS 583 

able plant food or moisture. The ridge from Black to Elephant Moun- 
tain is likewise of this character. 

In addition to the fault valleys just described are a second set of 
valleys of quite different characteristics and origin. These exhibit 
broad expanses with gentle slopes and a mature topography. They 
depart from the courses common to the fault type of valley and are 
generally arranged in two lines, north-south and east-west. The valley 
of Schroon Lak,e, parts of the valley of Lake George, and the valley 
of the Hudson are of this type. The mature characteristics of these 
valleys suggest far greater age than the fault valleys of more recent 
origin. They may date back to early geologic time and represent 
ancient valleys which have not suffered that wholesale transformation 
of character and direction that the fault valleys appear to have experi- 
enced through the agency of faulting and associated forces. 

GLACIAL EFFECTS 

The faulted and jointed character of the eastern half of the iVdiron- 
dacks enabled the ice of the glacial period to produce marked topo- 
graphic effects. The faults and associated escarpments were freshened 
by plucking and the relief was heightened, while the valleys, which in 
the main represent the loci of the faults, were in some instances deepened 
and steepened, in others deeply filled with drift. Certain drainage 
changes were also effected by the glacial ice. Some streams, as the 
Sacondaga, a tributary of the Hudson, and the upper Hudson itself, were 
turned aside from their preglacial valleys and caused to flow across low 
preglacial divides. Glacial drift was accumulated almost everywhere 
along the valley floors and spread as a thin mantle over the hill slopes, 
thinly on the steeper slopes and sometimes to considerable thickness on 
the marginal terraces.^ 

The greater part of the drift in the Adirondacks is stratified and is 
in the form of deltas and sand-plains; morainic material is scarce. 
This is due to vigorous ice movement in the glacial period and to the 
fact that the late glacial events were associated with submergence in 
the Mohawk, St. Lawrence, and Champlain valleys. A small number 
of local valley glaciers existed after the withdrawal of the main ice 
sheet from the region and formed (i) local moraines which overlie the 
stratified drift, and (2) cirques at the valley heads. 

1 For a general description of the Adirondacks see J. F. Kemp, The Physiography of the 
Adirondacks, Pop. Sci. Mo., March, 1906. See also for rock character and structural relation, 
Van Hise and Leith, Adirondack Mountains, in Pre-Cambrian Geology of North America, 
Bull. U. S. Geol. Surv. No. 360, 1910, pp. 597-621. 



584 FOREST PHYSIOGRAPHY 

CLIMATE AND FORESTS 

The greater height of the Adirondacks over the surrounding regions 
causes the precipitation to be decidedly greater. It is almost twice as 
great as in the lowland district in the western part of the state. In con- 
trast to the temperature maxima of 100° and over, in the Hudson and 
Mohawk valleys, the summer maxima of the Adirondacks are so low 
that there is seldom a day that is uncomfortably warm. The winter 
minima are lower, of course, than elsewhere in the state. In January, 
1904, when the minimum in New York City was —1°, the temperature 
was — 26° at Binghamton in the plateau of southern New York, eleva- 
tion about 850 feet, while in the Adirondacks, at Saranac Lake, about 
1500 feet above the sea, it was 46° and probably much lower in the 
higher points.^ 

The influence of the greater height and lower temperature of the 
central portion of the Adirondacks is strikingly brought out in any 
detailed map of the forest regions, on which is represented an island 
of northern spruce forest surrounded by hardwoods which occupy the 
St. Lawrence, Mohawk, and Hudson-Champlain depressions that rim 
completely about the tract. To the temperature factor is due the 
primary grouping of the forests of the region, while secondary influences 
are the irregular distribution of the drift and the steepness of slope as 
determined (a) by glacial erosion along the main valleys and (b) by 
faulting along the margins of the great crust blocks that form the prin- 
cipal mountain units in the more rugged portions of the Adirondacks, 
notably along the southeastern border. 

The predominating trees of the Adirondack forest - are spruce, hemlock, 
and balsam. There are also scattered individuals and groves of pine 
on the mountain slopes and cedars on the lake shores and in the swamps. 
Tamarack grows on the beaver meadows, dense tangled thickets of alder 
border the rivers, and birch and poplar are scattered here and there on 
mountain slopes and valley bottoms. Patches of maple, beech, and 
birch grow on tracts that have been bared by fire, wind, or lumbermen, 
and are the only important hardwood types that the region supports. 

1 A. J. Henry, Climatology of the United States, Bull. Q. U. S. Dept. of Agr., Weather 
Bureau, igo6, pp. 176-177. 

2 C. H. Merriam, The Mammals of the Adirondack Region, 1884, p. 21. 



CHAPTER XXVIII 

APPALACHIAN SYSTEM ^ 
{Introductory to the four succeeding chapters) 

General Features, Subdivisions, and Categories of Form 

The Appalachian System, Plate IV, includes the highest, roughest, best 
watered, most densely forested, and some of the most thinly populated 
sections of the eastern half of the country. Except the Adirondacks no 
other part of the eastern half of the United States has slopes of so great 
declivity and streams of such steep gradients. For a long time the 
western movement of the American colonists was hindered by the 
rough barrier of the Appalachians, and communication across their 
roughest sections is still difficult. In their remoter coves and valleys, 
as in the mountains of western North Carolina and those of eastern 
Kentucky, rude mountaineers still follow customs and employ a speech 
as unlike those of the valley peoples about them as the topography and 
soil of the one situation are unlike those of the other. 

The earliest settlers found the land covered with a great forest mantle; 
it was an almost illimitable wilderness of forest-covered hills and moun- 
tains. 

"Up to the doorsills of the log huts stretched the solemn and mysterious forest. There 
were no openings to break its continuity; nothing but endless leagues on leagues of shadowy, 
wolf-haunted woodland. . . . On the higher peaks and ridge crests of the mountains there 
were straggling birches and pines, hemlocks and balsam firs; elsewhere oaks, chestnuts, hickories, 
maples, beeches, walnuts, and tulip trees grew side by side with many other kinds. The sun- 
light could not penetrate the roofed archway of . . . leaves; through the gray aisles of the 

1 The term "system" is here employed to denote the whole territory affected by related 
mountain-making movements through successive geologic periods, whether these are in the 
nature of plateau uplifts or acute mashing and folding in restricted belts. Since crustal move- 
ments of sufficient magnitude to produce mountains in many cases result in the uplift of border- 
ing areas of some extent many belts of acute deformation are bordered by transitional upland 
belts. Though included in a system they are set apart as separate provinces from the moun- 
tain ranges formed upon rock belts of great structural comple.xity. Thus the Appalachian 
Plateaus and the Piedmont Plateau are included in the Appalachian System. The former was 
only slightly and locally deformed, then peneplaned, and later uplifted unevenly. Dissection 
of the more highly uplifted portions has been so deep as to give a relief of mountainous propor- 
tions — West Virginia and eastern Kentucky. Since peneplanation in the Tertiary the Pied- 
mont Plateau has sufltered only moderate uplift and dissection. It is an extensive upland 
whose inclusion in the Appalachian System is based not only on its former participation in 
older mountain-making movements but also on its participation in later and broader uplifts 
common to the whole territory between the Prairie Plains and the Coastal Plain. 

58s 



586 FOREST PHYSIOGRAPHY 

forest men walked always in a kind of midday gloaming. . . . Save on the border of a lake, 
from a clifftop, or on a bald knob . . . they could not anywhere look out for any distance. 
All the land was shrouded in one vast forest. It covered the mountains from crest to river 
bed, filled the plains, and stretched in somber and melancholy wastes towards the Mississippi." » 

To-day the forester finds great interest in the possibilities which the 
region suggests as to the scientific treatment of soils and trees, nowhere 
more important than in a rough country where the soil is thin and its 
maintenance bound up with the care of the forest. Some of the most 
baneful effects of excessive forest cutting are illustrated in the Appa- 
lachians. This great forest has been, and even now is, a great source of 
wealth, but its exploitation is attended by such a disregard of the in- 
fluence of deforestation upon the soil as to affect not only its produc- 
tivity but also its very existence. The sociological and political aspects 
of the forestry problems which await solution here are no le^s interesting 
than the scientific aspects. The increasing demands for greater food 
supplies on the part of a rapidly growing population are now extending 
the areas of cultivated land at the expense of the forest just as in the 
past. The state may say how far this shall go; whether clearings shall 
be made or not; prescribe the conditions of forest cutting; control fires; 
and guide the population along lines of greatest practical economy. 
These activities are involved in the question of the Appalachian forest 
reserves. It is implied in the argument for their maintenance that the 
state should exercise proper political means for securing the best scien- 
tific results; on the other hand is the contention that local experience 
will guide developmental projects along proper lines. With the pohtical 
aspects we have here nothing to do; the groundwork for an under- 
standing of the scientific aspects lies in a comprehension of the con- 
ditions of drainage, relief, and soils, which are the chief themes of the 
succeeding sections. 

The territory east of the lower Mississippi River consists of six differ- 
ent physiographic provinces — the low and poorly drained Mississippi 
Valley, the forest-clad Appalachian Plateaus, the parallel and regu- 
lar mountains of the Great Appalachian Valley, the irregular, forested, 
and narrow Appalachian Mountains, the gently undulating Piedmont 
Plateau, and the low, flat-lying Atlantic and Gulf Coastal Plain. The 
rocks of the Mississippi Valley are nearly horizontal limestones, shales, 
and sandstones deeply covered with river alluvium. Fig. 210; those of 
the Appalachian Plateaus are similar except that they are more sandy 
and have been lifted to a higher altitude, with the consequence that 
they are more deeply dissected. In the Great Appalachian Valley the 

• 1 Theodore Roosevelt, The Spread of English-speaking Peoples (in The Winning of the West), 
ed. of 1905, vol. I, pp. 146-147. 



APPALACHIAN SYSTEM 



587 




Fig. 23Sa. — Drainage map of the Appalachian region. 



rocks have been folded into long, symmetrical, parallel folds which 
are among the most notable physiographic features in the world. 
In the Appalachian Mountains and the Piedmont Plateau the rocks are 
chiefly schists, gneisses, and granites of extremely complex structure,, 
— ancient crystalline rock deeply decayed and mantled with residual 



588 FOREST PHYSIOGRAPHY 

soil. Seaward from the Piedmont Plateau and on both the Atlantic 
and Gulf slopes of the Appalachian and Ozark districts is a vast coastal 
lowland, the Atlantic and Gulf Coastal Plain. 

The lines of division between these physiographic provinces are 
everywhere topographically distinct except in the case of the common 
border of Piedmont Plateau and Coastal Plain. Although the latter is 
everywhere lower than the former, yet on the common border it is but 
little lower; and more distinct than the differences in topography are the 
differences in soils and the steeper descents of the eastward-flowing 
streams on passing from the Piedmont to the Coastal Plain. 

The great Appalachian System includes the four central members of 
the series of six between the Mississippi and the Atlantic coast. It extends 
roughly from the Ohio Valley on the northwest to the Atlantic Coastal 
Plain on the southeast and from the St. Lawrence Valley on the north 
to central Alabama and Georgia on the south. Its subdivisions and 
border relations on the north are somewhat different from those on the 
south. The Coastal Plain terminates at Cape Cod, north of which the 
Older Appalachians extend to the coast. A narrow upland plain, cor- 
responding to the Piedmont Plateau of the south, borders the southern 
and eastern margins of -the Green Mountains and extends from western 
Connecticut through Massachusetts and Vermont. The Green Moun- 
tains correspond to the Great Smokies, Unakas, etc., and the valleys 
of the Hudson and the Champlain are the counterparts of the Tennessee 
and the Coosa respectively at the south. The Catskills and the Cum- 
berland Plateau are also corresponding elements. The White Mountains 
and bordering uplands are exceptional features in that they have no 
southern representatives. At the south there is a single mountain and 
a single plateau element in the Older Appalachians; at the north there 
are two mountain axes and two bordering upland plains with a great 
valley — the Connecticut — between them. 

In general the Appalachian System includes two great belts composed 
of broadly different rock types — a southeastern belt composed chiefly 
of crystalline rock and a northwestern belt composed chiefly of sedi- 
mentary rock, Plate V. Both trend northeast and both have their 
broadest development toward the southwest. The crystalline belt, 
called the Older Appalachians, includes the Piedmont Plateau and the 
Appalachian Mountains; the sedimentary belt embraces the Newer 
Appalachians, including the Great Appalachian Valley (in places so filled 
with even-topped ridges as to be a mountain and not a lowland belt) 
and the Appalachian Plateaus, a group name for a number of separate 
plateaus such as the Cumberland Plateau, Allegheny Plateau, etc., and 



APPALACHIAN SYSTEM 



589 



interrupted by local basins such as the Nashville Basin and the Blue 
Grass Country. A knowledge of the geographic positions and relations 
of these members is indispensable for the further discussion of their 
physiography, Fig. 235a. 

The various provinces of the Appalachian System stand in a very interesting geologic rela- 
tion to each other, a relation that is of physiographic importance chiefly through its effect 
upon the drainage. While the details of this relation are complex the essentials may be 
roughly outlined £^s follows. The southeastern crystalline belt has very irregular structures 
which were gained during several pre-Paleozoic and Paleozoic mountain-making periods that 
deformed the strata and elevated the mass of the province. This whole area has been called 
the Older Appalachians in contradistinction to the Newer Appalachians formed upon the 
regularly folded strata. i 

The Older Appalachians existed as a narrow land area of unknown limits eastward but 
bordered on the western side by an arm of the sea that spread over a large portion of the cen- 



Ancient Continent 



Folded Zone 







^•^^-^VjJk^ATflS ^ .^h r g^a£::a^i^^af£K ^f.'^S£:;:ss£r7^ra^.To^^T^^^ ' ""- "^ 



Restoration of relations of land and sea and of position of strata prior to folding 



Fig. 236. - 



-Structural Relations of the various parts of the Appalachian System, looking south. 
(Willis, U. S. Geol. Surv.) 



tral lowland of the continent. The erosion of the Older Appalachian land mass gave rise 
to land waste that was swept into the neighboring seas. On the east the sediments then accu- 
mulated have since been buried and are now concealed by Cretaceous and Tertiary strata of 
later origin; on the west the heavy marine and fresh-water sediments accumulated in great 
beds which were (i) somewhat regularly folded at the end of the Paleozoic era to form the 
Newer Appalachians or (2) broadly uplifted to form the Appalachian Plateaus. The folding 
force was directed westward, so that the folds are in general more compressed, more notably 
faulted, and the dips steeper on the eastern than on the western margin of the Newer Ap- 
palachians. On the western border in fact the folds die out gradually. Cumberland Plateau, 
Walden Ridge, and other forms are flat synclines, while the Sequatchie Valley occupies an eroded 
anticline, and low folds of similar nature occur elsewhere within the eastern border of the 
Appalachian Plateaus, as in the Tioga and Elkland districts of north-central Pennsylvania. 
On the whole, however, the change from the strongly folded to the gently folded rocks of the 
1 W. M. Davis, The United States, Mill's International Geography, 1900, pp. 727-729. 



590 FOREST PHYSIOGRAPHY 

northwestern sedimentary belt is rather sharply locaUzed along a line now represented by 
the eastward-facing escarpments known on the south as the Cumberland Escarpment and on 
the north as the Allegheny Front. 

It must not be supposed that the strata of the Appalachian Plateaus are flat merely be- 
cause the strongly developed features of the Newer Appalachian belt east of them practically 
cease along the definite line indicated. They are often sensibly flat, but never absolutely level 
over considerable areas. Low folds occur here and there and a number of important faults 
have also been identified. 

These distinctions between the various belts of the Appalachian System serve a useful 
purpose in making physiographically simple what is geologically very complex. While the 
student may require for very detailed geographic and geologic work a minute knowledge of 
the geologic history of, for example, the Older Appalachians, the general features of the belt 
become very simple if the net results of all the complex history and not the details of the history 
itself are kept in mind. The broad features of the region have been developed with striking 
uniformity upon a mass of greatly deformed strata; the detailed topography and drainage are 
minutely irregular and reflect the detailed structural features. The broad features of struc- 
ture and origin are of chief importance in the present connection, but we shall nevertheless 
keep in the background of our thought the fact of geologic complexity in order that the more 
detailed descriptions that follow may be adequately explained. 

It is possible to assign all the topographic forms of the Appalachian 
System to a few simple categories, (i) The uplands and the even crest 
lines of the ridges are remnants of a Cretaceous peneplain above which 
are (2) hills and mountains — Unakas and Great Smokies on the south, 
White and Green mountains on the north, etc. — that have survived 
as residuals. (3) The third category includes the slopes, valleys, and 
open lowlands sunk into the Cretaceous lowland after its elevation in 
early Tertiary time. If the valleys and lowlands were tilled up to the 
level of these remnants and the whole surface depressed to a lower 
level we should have a representation of the geography of the tract 
near the end of the Cretaceous period. (4) This category includes those 
locally base-leveled areas of small extent developed in late Tertiary 
time. They are much more limited in extent than the early Tertiary 
lowlands and were developed only upon the softest rocks near the 
largest streams. (5) The fifth category includes the narrow and young 
trenches and valleys with their associated terraces below the level of 
the late Tertiary peneplain.^ 

Physiographic Development 
The physiographic development of the great Appalachian System 
has been complicated by great variations in structure, by pronounced 

1 W. M. Davis, The Geologic Dates of Origin of Certain Topographic Forms on the Atlantic 
Slope of the United States, Bull. Geol. Soc. Am., vol. 2, 1891, pp. 578-579. The assignment of 
the relief forms to categories was first clearly brought out in the paper cited; but the number 
of the categories is increased here to include the fact of a third local peneplanation later than 
the early Tertiary, — a local peneplanation resulting in the development of a topographic level 
identified by Hayes, Campbell, and others in the Chattanooga di.strict as the Coosa pene- 
plain, in the Nashville basin as the Nashville peneplain, in western Pennsylvania as the 
Worthington peneplain, in northern New Jersey as the Somerville peneplain, etc. 



APPALACHIAN SYSTEM 59 1 

differences in elevation, and by the varying distances of different dis- 
tricts from the sea. Many features of the topography are unified, how- 
ever, through their association with the most important single fact 
related to the system, the fact of former peneplanation. This makes it 
necessary always to keep in mind two groups of facts, those which make 
for diversity and those which make for uniformity of topographic 
expression. 

On the wholp the province has been a land area since the close of the 
Carboniferous period and in all that time has been a region of erosion. 
The uplifts which gave rise to erosion were not simple but complex and 
were probably halted a number of times by depression, so that the 
present altitude of the region represents the algebraic sum of a number 
of uplifts and depressions. The uplifts do not appear to have been 
regular but intermittent, for, as we have just seen, the surface was stable 
during several periods long enough to allow the formation of either 
extensive or local peneplains. 

A remarkable feature of the province is the unity of expression and 
origin of a large number of the most prominent topographic forms. 
Related features are continued over a wide area throughout Ala- 
bama, Tennessee, Kentucky, West Virginia, Georgia, North Carolina, 
South Carolina, Virginia, and Maryland, and indicate that the con- 
ditions that produced them must also have been uniform over wide 
areas. ^ 

The most widely distributed feature is the Cretaceous peneplain that 
constitutes the highest surface of reference in the province. It is also 
the oldest topographic feature that can be identified with certainty 
and is a plane of reference for the forms of later origin. The rem- 
nants of the Cretaceous peneplain are sufiiciently numerous so that 
a number of important generalizations can be determined. It is the 
most perfectly base-leveled surface ever developed in the tract and was 
exceptional for its extent and regularity. It must not be supposed, 
however, that its surface was perfectly horizontal. It was most nearly 
level where erosion progressed under highly favorable conditions, as 
near the sea margin, or along the largest streams, or where the rocks 
had httle power of resistance to weathering and erosion. In favorable 
localities hard and soft rocks were reduced to a common level and the 

1 For details see (i) Hayes and Campbell, Geomorphology of the Southern Appalachians, 
Nat. Geog. Mag., vol. 6, 1894, PP- 63-126; (2) C. W. Hayes, Physiography of the Chattanooga 
District in Tennessee, Georgia, and Alabama, 19th Ann. Rapt. U. S. Geol. Surv., pt. 2, pp. 
9-58; (3) Bailey Willis, The Northern Appalachians, Nat. Geog. Mon., 1896, pp. 169-202; 
(4) W. M. Davis, The Geologic Dates of Origin of Certain Topographic Forms on the Atlantic 
Slope of the United States, Bull. Geol. See. Am., vol. 2, 1891, pp. 545-586. 



592 FOREST PHYSIOGRAPHY 

rivers flowed in meandering courses and with slow currents across the 
underlying deeply weathered and soil-covered strata. 

The outcrops of the harder strata or the originally higher masses 
were generally developed in relief upon the Cretaceous peneplain, 
especially in the case of those located on broad divides distant from 
the sea. In western North Carolina and northern New England, for 
example, subdued mountains stood at altitudes varying from 3000 to 
3600 feet above sea level and somewhat less than this amount above 
the level of the adjacent portions of the Cretaceous peneplain. The 
map, Fig. 237, brings out clearly the unreduced portions of the land 
surface that projected above the general level of the Cretaceous pene- 
plain. Such areas were on the whole relatively small, and although 
they were not reduced to the general level they were eroded to such 
a degree as to stand at only moderate elevations. Their present height 
is due to later upKft and the development of local or partial pene- 
plains as well as deep valleys below and around them. They consti- 
tute, for example, the highest portions of the Blue Ridge on the western 
border of the Piedmont Plateau and the groups of higher mountains, 
principally in western North Carolina, the Great Smoky Mountains, 
the Unakas, the Iron Mountains, the Pisgah range, etc. 

Among the mountains the forces of erosion were able to reduce local 
tracts only, thus giving rise to prairie-like country among the moun- 
tains, adjacent river basins being separated in many instances by low 
divides. Such a locally base-leveled surface is found all the way from 
Roanoke to Cartersville, Virginia, in the heart of the Smoky Mountains. 
The upper basins of the Coosawattee and Etowah, Georgia, consist of 
broad undulating plains partly enclosed by mountains; island-like resid- 
uals with gentle slopes rise above the level of the plains. 

Later erosion has in many instances completely destroyed the Cre- 
taceous peneplain over wide areas, and this is true in general around 
the margins of the province, but especially in central Tennessee and 
Kentucky, where the uplift of the peneplain brought about its destruc- 
tion over wide areas, so that there are only a few widely separated 
outliers of the Cumberland Plateau whose summits still indicate the 
surface of the peneplain. A typical outHer of this kind is Short Moun- 
tain in central Tennessee, which rises a thousand feet above the sur- 
rounding plain. It is 20 miles from the Cumberland Plateau, has the 
same altitude, and is capped by the same hard sandstone. The low 
plain intervening is formed upon limestone which was easily eroded upon 
the removal of the sandstone cap. In eastern Pennsylvania, portions 
of southern New England, and over the greater portion of the Piedmont 



APPALACHIAN SYSTEM 



593 



Plateau the Cretaceous peneplain has also been dissected in the forma- 
tion of local peneplains at lower levels. 

That the uplifted Cretaceous peneplain is with certainty recognizable 
so long after its uplift is due to the fact that interstream surfaces which 
are in the aggregate of great areal extent waste very slowly. The rivers 
of a region denude the land surface by relatively small amounts, for 
most of the land is not occupied by streams. Wasting takes place 
chiefly through rain-wash, infinite gullying, and slumping, etc., so that 
the interstream surfaces, less affected by these forces, may carry clear 
records of denudation cycles long closed. 

The uplift of the oldest topographic level, the Cretaceous peneplain, 
has been accomplished in large part by a series of deformations of true 




Coastal 
Plain 



Bordering 
Plateaus 



Great Appalachian 

Valley 



Areas Not reduced 
to baselevel 



Fig. 237. — Axes of deformation represented by broken lines, AB, CD, EF, GH, and OP. Contours 
represent elevations of restored surface. (Hayes and Campbell.) 

orogenic character affecting comparatively narrow areas along certain 
well-defined axes. One of the most important of these is that which 
extends from Cincinnati to Cape Hatteras, a transverse uplift which 
is believed to have a prominent part in the great projection of Cape 
Hatteras, on the eastern side of the United States. A second and more 



594 FOREST PHYSIOGRAPHY 

closel}'- defined axis of elevation extends from Chattanooga to Cin- 
cinnati. A third prominent axis passes near Atlanta and forms a 
tangent to the great northwestward bend of the Tennessee. In the 
northern part of the Appalachian System the restoration of the remnants 
of the Cretaceous and Tertiary peneplains shows an axis of deforma- 
tion in western Pennsylvania, as shown in Fig. 238. This deformation 
was in the nature of a broad bowing up of the earth's crust along a 
southwest-northeast axis which appears to be parallel to or continuous 
with the axis that passes through the summit of the Cumberland 
Plateau. A similar pronounced axis is recognizable in western Massa- 
chusetts and Connecticut and corresponds to the structural axis of the 
Green Mountain range. 

The orogenic movements which deformed the surface of the peneplain 
determined the concentration of erosional energy along certain axial 
lines indicated on pp. 593 and 688. Where the elevation was slow ero- 
sion was moderate; where the elevation was rapid erosion was rapid 
and the peneplain was here quickly dissected. 

The movements which terminated the Cretaceous cycle of erosion 
inaugurated the succeeding or early Tertiary cycle of erosion. The 
crust of the earth was maintained at a fairly constant elevation so long 
that the surface was again reduced to a peneplain in those regions 
where conditions of erosion were exceptionally favorable. Broad valleys 
developed upon soft rock belts of the interior portions of the southern 
Appalachians were reduced to base-level lowlands. The Harrisburg 
peneplain, standing about 500 feet above the sea, east of Harrisburg, 
Pennsylvania, is the northern representative of this erosion level. 
Like the Cretaceous peneplain, the early Tertiary peneplain has been 
greatly modified by erosion and by uplift, which carried both the Cre- 
taceous and early Tertiary peneplains above their former level. The 
second uplift introduced a third or late Tertiary cycle of erosion, which 
had progressed to an even less advanced stage than its immediate prede- 
cessor when uplift again intervened and brought the land approximately 
to its present level. After this level was attained erosion partially 
destroyed the latest peneplain and continued the destruction of the two 
higher peneplains. 

In a sense it is incorrect to speak of the two Tertiary lowlands as peneplains, for a relatively 
small portion of the whole region was reduced to base level. They are, strictly, local pene- 
plains, and the durations of the erosion cycles they represent were very short as compared with 
the duration of the Jurassic-Cretaceous cycle. 

The Cretaceous peneplain is called the Cumberland peneplain at the 
south and the Kittatinny (sometimes Schooley) peneplain at the north 




( MAPSHOWINGTHERELAI ".ECE 



EFi rif. FOFTHECH 



Yig. 23S. — Darkest areas, base-leveled areas of the late Tertiary or Coosa peneplain; lightest shade, early 
Tertiary or Highland Rim peneplain; intermediate shade, remnants of the Cretaceous or Cumberland 
peneplain. Residuals above the Cumberland peneplain are shown in slightly darker shade. Scale, 
20 miles to the inch. (Hayes, U. S. Geol. Surv.) 

59S 



596 FOREST PHYSIOGRAPHY 

(Pennsylvania, New Jersey, etc.), in the former case because the sum- 
mit of the Cumberland Plateau is the best preserved remnant of it, in 
the latter case because the even crest of the Kittatinny Mountains of 
northern New Jersey is due to its former development in that district. 
The early Tertiary peneplain is called the Highland Rim peneplain at 
the south because well preserved beyond (west of) the edge of the Cum- 
berland Plateau on a surface called the Highland Rim, with respect to 
the Nashville Basin below it; the same level is called the Harrisburg 
at the north because well developed east of that city. For compar- 
able reasons the late Tertiary peneplain is called the Coosa at the 
south and the Somerville and Worthington at the north. We shall 
generally refer to these three peneplains as Cretaceous, early Tertiary, 
and late Tertiary, implying their correlation over the whole Appa- 
lachian System. The student will find reference to them facilitated by 
the use of these terms instead of the local names ordinarily employed. 

Relation of Topography to Rock Types 

Since lithology and rock structure control topographic form to a large 
degree during the youthful and mature stages of landscape development, 
it is of fundamental importance in the study of the Appalachian region, 
where vigorous erosion is now going on, to determine the principal rock 
types and their degrees of erodibility. In the southern part of the 
Appalachian System the beds of conglomerate, quartzite, and siliceous 
shale are composed of nearly insoluble materials that powerfully resist 
erosion. The outcrops of these rocks are marked by high ridges, as in 
Beans Mountain, an outlier of the Unakas, and Indian and Weisner 
mountains south of the Coosa River. 

The limestones alternating with more or less calcareous shales are 
in general easily eroded, a large part of the erosion being by solution. 
Portions of them have sufficient resistance to erosion to stand as some- 
what higher ridges, but both the height and the number of such ridges 
are nowhere great. One of the members of the limestone group is the 
Knox dolomite, which contains a large proportion of relatively insoluble 
chert which, on the removal of the more soluble calcium carbonate, re- 
mains behind as a heavy residual mantle that has a protective influence 
on the remaining portion of the formation, thus giving rise to moder- 
ately high hills and irregular ridges. 

A third group of rocks (Silurian, Devonian, and Carboniferous) con- 
sists of sandstone and chert of great resistance to erosion. These strata 
therefore stand out in some localities as residuals of superior height, 



APPALACHIAN SYSTEM 597 

for example, Oak and Chattanooga mountains. Chert beds have also 
been instrumental in preserving the Highland Rim. 

The Coal Measures conglomerates, sandstones, and sandy shales form 
a group with distinct topographic characteristics. The conglomerate is 
the most resistant member and constitutes the cap rock of much of the 
Cumberland Plateau and the most important factor in the long preser- 
vation of its base-leveled surface. These various rock groups as a whole 
show a tendency to grow thicker and less calcareous toward the south- 
east, so that in a few cases strata of the same age weather into en- 
tirely different topographic forms on the two sides of the district. 

The igneous and metamorphic rocks of the region contain a large 
proportion of feldspar and may be designated the feldspathic group. 
The feldspar which they contain is an element of weakness, for on ex- 
posure to the weather it decays quite rapidly, and the rock of which it 
is a part disintegrates. The Piedmont Plateau is composed largely of 
such easily weathered feldspathic rock, chiefly igneous, and a number 
of large valleys in the mountainous portion of the crystalline rock belt, 
of which Mountaintown and Talking Rock valleys are illustrations, owe 
their existence to the occurrence of large areas of highly feldspathic 
rock. It is not uncommon to find granite and diorite with a high per- 
centage of feldspar weathered to depths of 50, 70, or 100 feet from the 
surface. 

On the other hand the slates, graywackes, and conglomerates of the 
metamorphic terranes are nonfeldspathic and have a high degree of 
resistance to weathering and erosion. They have as a rule been greatly 
deformed, standing on edge in much of the mountainous section of the 
southern Appalachians. The result of combined hardness and vertical 
or nearly vertical position is shown in long, narrow, steep-sided ridges, 
or in rather sharp and high peaks with many radiating finger-like spurs 
separated by narrow, V-shaped valleys, a type of irregular topography 
seen to good advantage at the southern end of the Unakas on the bound- 
ary between North Carolina and Tennessee. The accompanying illustra- 
tion, Fig. 239, brings out the relation between the topography on the one 
hand and the composition and erodibility of the rocks on the other. 
The relative thicknesses of the different groups is indicated by the vertical 
distances, relative erodibility by the lengths of the horizontal lines. 

A similar relation between rock types and topography is exhibited in 
the northern and central portions of the Appalachian System. In the 
zigzag ridges of Pennsylvania the hard ridge makers are thick, hence the 
mountain feature is strongly developed; in the lowlands of the Hudson 
east of the Catskills the soft formations are thick, the hard forma- 



598 



FOREST PHYSIOGRAPHY 



rt in 

^8 



S. Coal Measures sandstone and conglomerate. 

4. Lower Carboniferous limestone. 

3. Chert and sandstone, lower Carboniferous, Devonian, and upper Silurian. 

. Chickamauga limestone. 



\ Knox dolomite. 



Cambrian limestone and shale. 



I. Cambrian quartzite. conglomerate, and siliceous shale. 



B. Nonfeldspathic rocks. 



A. Feldspathic rocks. 



Fig. 239. — Curve illustrating the relation of topographic relief to lithologic composition in the southern 
part of the Appalachian System. The term unaka is applied to a massive residual, monadnock to an 
isolated residual surmounting a peneplain. Each curve toward the left denotes a less resistant rock, 
each curve toward the right a more resistant rock. (Hayes, U. S. Geol. Surv.) 



APPALACHIAN SYSTEM 



599 



tions thin, hence the lowland feature is strongly developed. The prin- 
cipal hard formations are the Pocono sandstone, the Oneida-Medina 
sandstones, and the Pottsville conglomerate; the soft formations are the 
Hudson River shales, the Mauch Chunk shale, and the Coal Measures. 
The Pocono sandstone forms Second, Peters, Mahantanago, Line, and 
Little mountains northeast of Harrisburg in the splendid series of zig- 
zag ridges developed there; the Oneida-Medina sandstone forms Blue 
Mountain in the same locality; and the Pottsville conglomerate forms 
Third Mountain and Big Lick Mountain. The intervening valleys are 
formed upon the soft formations, principally upon the Mauch Chunk 
shales and the Coal Measures, as in the case of the upper valleys of 
Mahonay and Shamokin creeks. These soft formations are narrow as 
compared with their development toward the north, and the valleys 
formed upon them are likewise narrow for the most part; in eastern 
New York they are thick and have weathered into broad valley lowlands. 



Glacial Effects 

Reference to the map, 51ate 
IV, will show that the northern 
part of the great Appalachian 
System was glaciated but that 
the southern and central por- 
tions were not covered with 
ice. It follows that the inter- 
pretation of the topography and 
drainage of the latter districts 
is much easier than in those 
regions where glaciation has in- 
terfered with the normal de- 
velopment of the landscape or 
has partially buried the surface 
underneath a cover of glacial 
till. 

One of the most important 
effects of glaciation was the 
changing of river courses either 
by the bodily diversion of 
streams, the ice occupying the valleys long enough to enable a new 
course to be cut by the river in a different situation, or by the block- 
ing of the preglacial channels with glacial drift, causing streams to be 
deflected into adjacent valleys. One of the most striking instances of 




#New Martinsville ,g( 



Fig. 240. — Probable preglacial drainage of western 
Pennsylvania, the limit of glaciation is shown by 
the broken crossed line. (Modified from Leverett.) 



6oo FOREST PHYSIOGRAPHY 

glacial diversion is that of the Allegheny, which formerly flowed north- 
ward into Lake Erie northwest of Pittsburg, Fig. 240. The continental 
ice sheet displaced the river and kept it to a southern course so long 
and so modified the ancient valleys by drift deposits that with the re- 
treat of the ice the streams had established themselves in new channels 
draining in the opposite direction and forming a system tributary to the 
Mississippi.^ 

Many other tributaries of the Ohio suffered similar changes of posi- 
tion and direction of flow through glacial action. The Ohio itself was 
in large part diverted from its preglacial channel. The variation in width 
of the present channel of the Ohio is the result of the formation of a 
single channel out of a number of sections of different stream channels. 
It is significant that the general course of the stream corresponds 
roughly with the southern limit of glaciation, a condition similar to that 
found in the course of the Missouri and due to similar causes. Under 
these conditions it is not surprising that the fall of the Ohio River is not 
uniform; it varies from 0.2 foot to at least 5 feet to the mile. The 
greater fall commonly occurs where the river crosses the old rock divides 
which are not yet reduced to a graded profile. The original courses of 
the streams of the till-covered country north of the Ohio have now been 
determined in some detail by borings for oil and gas. Well records 
are so numerous in the region as to enable faithful restorations of the 
bedrock surface and the character of the drainage. Those streams 
which discharged northward toward or against the ice margin also 
suffered extensive modifications too intricate to examine in detail in 
this connection.^ 

In at least one locality the ice had an important effect in impounding 
the drainage of a district and causing the formation of lake clays and 
marginal deltas now at some height above the drained lake floor. Lake 
Passaic, an extinct glacial-marginal lake of northern New Jersey, Lake 
Neponset in eastern Massachusetts, and many other similar lakes in 
central New York are illustrations in point. Lake Passaic was formed 
within (west of) the curved Watchung trap ridges and its extinction 
followed upon the disappearance of the ice and the cutting down of the 
outlets. The chief importance of such phenomena to the student of 
forest physiography Hes in their relation to the character of the soil; 

' Topographic and Geologic Survey of Penn., 1906-1Q08, pp. 123-124. 

2 For a discussion of both typical and detailed features see W. G. Tight, Drainage Modi- 
fications in Southeastern Ohio and Adjacent Parts of West Virginia and Kentucky, Prof. 
Paper U. S. Geol. Surv. No. 13, 1903, who discusses the changes in the courses of the rivers 
of the region, reconstructs the old courses, and analyzes the causes that have led to the drain- 
age changes. 



APPALACHIAN SYSTEM 



60 1 



an understanding of the distribution of the bottom clays and the gravelly 
and sandy beach and delta deposits rests upon a knowledge of the 
existence and extent of a former lake. 

While the northern ends of both the Older and the Newer Appalachians 
were glaciated, Plate IV, the topographic effects of glaciation are of 
minor importance. The preglacial relief is still prominent in valley and 
upland while the glacial relief is in the nature of minor irregularities — 




BoundBrook 



Fig. 241. — Maximum stage of Lake Passaic. All outlets except that at Moggy Hollow 
were either blocked by ice or filled with drift. (U. S. Geol. Surv.) 



the detailed features of valley slopes and floors and the drumlins, eskers, 
sand plains, and low morainic ridges scattered irregularly about. 

The amount of till deposited by the ice sheet in the Appalachian 
Plateaus is very slight. This is due to the brief period in which the 
ice overlay the region, to the elevated nature of the country ,*and to the 
fact that hard rock yielding little waste constitutes the cap rock of a 
large part of the province. The valleys received the chief contributions 
of drift, and many of them are also partially filled with fluvio-glacial 
deposits now terraced by the streams. The terraces occur without as 



6o2 FOREST PHYSIOGRAPHY 

well as within the southern border of the glaciated country and are 
among the most conspicuous and persistent elements of the valley 
forms. 

Detailed features of relief and drainage that owe their origin to gla- 
ciation will be discussed in connection with the general physiography 
of the various regions of the Appalachian System. 



CHAPTER XXIX 
OLDER APPALACHIANS 



SOUTHERN APPALACHIANS AND PIEDMONT PLATEAU 

Appalachian Mountains 

The southeastern belt of crystallines in the Appalachian System con- 
sists of two very unlike portions, a western portion of strong relief, the 
Appalachian Mountains, and an eastern of low relief, the Piedmont 
Plateau. The mountain belt is broad at the south and narrow at the 
north. In western North Carolina, northwestern South Carolina, and 
eastern Tennessee the Appalachian Mountains are 50 miles wide and 
are bordered by declivities of the first order; in western Virginia, central 
Maryland, and south-central Pennsylvania the belt narrows to a single 
ridge known in its various parts as the Blue Ridge (Virginia), Catoctin 
Mountain (Maryland), and South Mountain (Pennsylvania). Farther 
north the Appalachian Mountains are represented by the highlands of 
New Jersey, the highlands of the Hudson, the Green Mountains, etc. 
These northern representatives of the system are narrow and their 
relief is not great as compared with the mountains of North Carolina, 
yet they have notable relief, for both the crystalline rocks and the Hme- 
stones, shales, and sandstones of varying structure and age that border 
them on either hand have been worn to lowlands, valleys, or upland 
plains of relatively slight relief. 

Attention will here be given chiefly to the mountains of the broad 
southern portion in western North Carolina and eastern Tennessee, 
whose most notable qualities as compared with other portions of the 
Appalachian Mountains are (i) their great height and ruggedness, (2) 
their great areal extent, and (3) their dense and valuable forests. This 
is by far the most important member of the southern Appalachian dis- 
trict and is here designated the southern Appalachian Mountains. 

The southern Appalachian Mountains include the highest point in 
the eastern half of the United States (Mount Mitchell, N. C, 671 1 
feet) and are more truly mountainous than any other portion of the 
country east of the Rockies. So unsettled are they that certain sections 
have only the merest sprinkling of population; and in general one finds 

603 



6o4 FOREST PHYSIOGRAPHY 

only scattered cabins and small clearings, except in a few localities where 
areas of less resistant feldspathic rock have enabled the forces of erosion 
to form rolling plains of limited extent or valley flats that permit more 
extensive clearings. 

The ridges and ranges of this mountain group nowhere display ex- 
ceptional declivities, and in few places may one find any approach to 
the wild mountain forms that usually attract the lover of mountain 
scenery. The mountains have never been glaciated, and cirques and 
broad, flat-bottomed, steep-walled valleys on a scale comparable to the 
higher valleys of the Sierra Nevada and Lewis mountains of the Pacific 
Cordillera are here wanting. The slopes have a smoothed and softened 
appearance enhanced by the dense forest cover, while the blue haze 
that hangs over the mountains perpetually gives the effect of great 
distance and height to ranges but a few miles away. 

The mountains of this group have suffered great erosion and have 
passed the point where they exhibit the profounder aspects of mountain 
scenery. On the whole they are topographically subdued and are well 
cloaked with waste except here and there where bare rock slopes may 
be seen. Furthermore, the drainage has become well adjusted to rock 
structure and hardness, the whole group being drained by an intricate 
and thoroughly ramifying system of streams. For example, the sides 
of the mountains in the Pisgah range are steep but are composed of 
smooth, flowing slopes and rounded crests as a rule free from cliffs. 
Lines of small cliffs and ridges occur only upon the harder and limited 
outcrops of an extremely resistant mica-gneiss. The granites make 
cliffs near drainage lines or along the slopes of the Blue Ridge, as at 
Caesar's Head. In general the even slopes of weathered rock of the 
mountain group are seldom broken and the cover of heavy forest is 
continuous on high and low ground alike. '^ 

The height, irregularity, swift drainage, and general ruggedness of 
the southern Appalachian Mountains are features which distinguish 
this mountain system only because of the contrast they afford to the 
flatness, fertility, easy cultivation, and good means of communication 
of the low, rolling, piedmont and coastal plains on the east and the 
broad flats of the great valley of eastern Tennessee on the west. As 
mountains go, the southern Appalachians are neither notably rugged 
nor lofty nor are they remote from the centers of consumption as are 
large tracts of equal size in the Pacific Cordillera, but they possess these 
qualities in sufficient degree to form a strong contrast to the other moun- 
tains of the eastern half of the United States. 

1 A. Keith, Pisgah Folio U. S. Geol. Surv. No. 147, 1907, p. i. 



\i i: I.I y.y map 
SOlTIIilUN Ari'Al.AClIIAN IfKCiloX 






^/ 




Plate III. — Soul? 



^^^^^^£n 




PLATE III 



I X N 



X 



'X^i 



Y ) 



Appalachians. 



OLDER APPALACHIANS (SOUTHERN DIVISION) 



60s 



Interest in the southern Appalachians is heightened by the fact that 
they contain one of the largest bodies of fine timber to be found on the 
Atlantic slope of the country and are of almost supreme interest to the 
eastern forester, who sees in them one of the country's greatest forestry 
possibilities. Nowhere else in the United States, not even excepting 
the arid and untimbered West, do the correlated problems of drainage, 
soil maintenance, forestry, and agriculture have a larger immediate 
importance or their solution a more far-reaching effect. In a region 
made up chiefly of steep mountain slopes each man's acts must be in a 




Fig. 242. — Pisgah Mountains from Eagles Nest near Waynesville, N. C, looliing S. 70° E. Cold 
Mountain (6000 feet) and Big Pisgah Mountain (5749 feet) are on the sky line. Beatty Knob in the 
middle distance shows characteristic details of spurs and ridges. (U. S. Geol. Surv.) 

high degree adjusted to the welfare of his neighbor if both have interest 
in the productions of the soil; each man must become his brother's 
keeper as a matter of economic as well as of moral necessity. * 

The distinctly greater elevation of the southern Appalachians above 
the surrounding country gives them a notably cooler climate. The 
temperature is that of south-central Pennsylvania or New Jersey. 
Above 5000 feet it ranges usually from 45° to 75° in summer and from 
— 10° to 45° in winter. The low temperature is expressed among other 
ways in the presence of red and black spruce, northern birch, white pine, 



6o6 FOREST PHYSIOGRAPHY 

and fir, while the magnolia, mulberry, papaw, and persimmon trees are 
representative southern species which occur at lower elevations and 
have reproductive associations with large areas of such species in the 
surrounding plains and valleys. 

Because of greater elevation, the degree of cloudiness and the rainfall 
are both much greater than on the surrounding plains and plateaus. 
This being the case we should expect also to find differences in the dis- 
tribution of these climatic conditions within the mountain area, on 
account of the rather wide topographic differences. The most im- 
portant generalization of this kind is in the distribution of heat and 
rainfall. The southeastern slopes, with a declivity of io° to 30°, are 
almost exactly normal to the sun's rays for several summer months 
and receive almost as much heat from the sun as do equatorial lands 
during the same period. The northwestern slopes depart from the 
normal by an equal amount but in the other direction, and may be said 
to receive an amount of direct insolation no greater than that received 
by Newfoundland or southern Norway, though in each case the net 
result is nowhere near such extreme temperatures as these comparisons 
would seem to show on account of the mitigating effects of the wind, 
which tends constantly to equalize the distribution of the heat. Never- 
theless the southeastern slopes are notably warmer than the north- 
western slopes, and being warmer are also drier on account of the greater 
evaporation. 

A second and more important cause for the comparative dryness of 
the southeastern slopes is the effect of the prevailing westerly winds 
which precipitate about 60 or 70 inches of rain on the windward (north- 
west) slopes and but 40 or 50 inches on the leeward (eastern) slopes. 
This climatic contrast is sufficiently marked to affect the distribution 
of forest fires, which are found to be much more frequent, or at least 
do the greatest amount of damage, on the drier southeastern slopes 
than on the moister northwestern slopes. About 80% of the total 
area, or 4,500,000 acres, have been burned over, the greater number of 
the fires being on the ridges, where they are often set to improve the 
pastures, or to effect partial clearings. 

Besides these differences in rainfall and temperature on the two 
slopes of the southern Appalachians there are important differences 
dependent upon altitude. These are roughly expressed on the accom- 
panying map showing the rainfall of the United States, but a larger 
number of observations would undoubtedly show even greater differ- 
ences, as have been shown by the refined observations of late years in 
the Alps of Europe and the mountains of Wales. 



OLDER APPALACHIANS (SOUTHERN DIVISION) 607 

PHYSIOGRAPHIC DEVELOPMENT 

The southern Appalachians have a very compUcated structure. The 
rocks are chiefly crystalline and are in part igneous, in part meta- 
morphic. The igneous rocks occur in the form of ancient dikes, sheets, 
etc. The metamorphic rocks consist of altered sedimentary strata which 
were deformed in several periods of mountain making but chiefly in the 
Ordovician • period when there was formed a very complex structure, 
the folds due to compression being arranged in all directions, though 
the northeast-southwest direction predominates. So complicated is the 
structure, and so diverse is the rock character within short distances, 
that great irregularity of drainage direction and of topographic form is 
the consequence. 

While irregularity of structure thus prevails there is a marked pre- 
dominance of trend toward the northeast and it is in a northeast-south- 
v/est direction that the principal stream courses, valleys, and ridges lie. 



Fig. 243. — Geologic structure of the Appalachian region where extreme faulting has occurred. Length 
of section, Sf miles. (Keith, U. S. Geol. Surv.) 

Structural irregularities are expressed in the many cross ranges, the 
highly irregular trend of mountain and range spurs, and the minute irregu- 
larities in the. slopes and crests of individual mountain ranges. The 
character of the rock also has been an important factor in making the 
slopes irregular in detail. The areas of softer rock such as the feldspathic 
Cranberry granite, extensively exposed about Asheville and in smaller 
areas in many other localities, weather down much more rapidly than 
less feldspathic rock, and as the outcrops of the former are extremely 
irregular, the dependent erosion forms are correspondingly irregular. It 
is therefore only in a broad view that the mountains appear to possess 
any system whatever, and even in such a view there are large tracts in 
which no general arrangement can be discovered. The larger members 
of the group, such as the Unakas, the Great Smoky Mountains, the 
Black Mountains, the Iron Mountains, the Pisgah range, and many 
others, all run in a northeasterly direction, Plate III, but this feature is 
less clearly seen in the details of the mountain slopes than in a general 
view of the ranges such as a group map affords. 

The smoothest contours in the southern Appalachians are in the 
southeastern portion, occupied almost exclusively by igneous rocks which 
have given rise to broad and massive domes; the northwestern portion 



6o8 



FOREST PHYSIOGRAPHY 



is carved out of metamorphic rock of greater resistance to erosion, and in 
contrast to the subdued mountain forms west of the Blue Ridge are the 
Unakas and Great Smoky mountains, whose peaks are prevaiUngly 
rather sharp and rise to greater heights. The summits of the Unakas 
are capped for the most part by hard quartzite; the mountains close to 
the Blue Ridge are carved out of massive granite. This adjustment of 
topography to the hardness of the rock is illustrated everywhere and is 
one of the features indicative of the great geologic age of the region, 
though, had the topographic cycle been carried farther, these adjust- 
ments would in their turn have given way to peneplanation in which 




Fig. 244. — Roan Mountain, Tenn. Hills in foreground are composed of granite; the broad rounded 
summits of the mountains are characteristic of the Roan gneiss. (U. S. Geol. Surv.) 

rocks of varying hardness all but cease to have topographic expression, 
as is the case in the Piedmont Plateau on the east or the Cumberland 
Plateau on the west. 

The absence of adjustments to structure is exhibited in the courses of 
the westward-flowing streams which in some instances cross the main 
mountains of to-day, the Unakas and Great Smokies, in deep gorges and 
canyons that divide these ranges into a number of more or less separate 
units. A certain degree of this transection is, however, to be attributed 
to upheaval of the mountains in the paths of the streams, an upheaval 
that continued during the two Tertiary uplifts that followed the develop- 
ment of the Cretaceous peneplain in the Appalachian region. As already 
described, these uplifts were sharply localized along the present moun- 



OLDER APPALACHIANS (SOUTHERN DIVISION) 609 

tain axes and were orogenic in nature, thus giving a certain antecedent 
quality to the westward-flowing streams. 

In the southern Appalachians the Cretaceous peneplain was de- 
veloped only upon the highly feldspathic rocks and the less altered 
slates, while the nonfeldspathic conglomerates and the harder slates 
formed considerable elevations above the peneplain. These elevations 
were sometimes of mountainous proportions, and were of such size and 
such degree of resistance to erosion and so favorably placed at the 
headwaters of the dissecting streams as to have suffered relatively little 
erosion since the uplift of the Cretaceous peneplain. The best-pre- 
served residuals are the Great Smoky Mountains, the Unakas, and a 
dozen or more neighboring groups.^ 

The largest and best-preserved remnants of the Cretaceous plain 
formed within the southern Appalachians are those about Asheville, 
where a local peneplain was developed upon the feldspathic Cranberry 
granite, and east and south of James Mountain and south of the Unakas 
in Mountaintown and Talking Rock basins. Over a large part of the 
southern Appalachians the Cretaceous level is expressed only in dissected 
remnants of a former plateau surface at the heads of the main streams 
as in the plateau immediately west of the Blue Ridge. Many smaller 
remnants of such a leveled surface are to be found here and there among 
the mountains, for example in the plateau of the French Broad River 
from 2200 to 2300 feet above the sea, and similar cases are to be found 
in a number of other river systems at comparable but slightly different 
altitudes. 

The plateau bordering Pisgah River near Waynesville and Sonoma is between 2700 and 
2800 feet above the sea; that of French Broad River is about 2200 feet. Remnants of the 
plateau west of the Blue Ridge pass entirely around the head of French Broad Valley and along 
the heads of the minor streams and continue southwestward across the headwaters of Toxaway 
and Horse Pasture rivers, which are tributary to the Atlantic. 

The valleys intervening between the mountain ranges of the Pisgah region are sharp, narrow, 
and V-shaped at their heads but widen out at lower levels where they are bordered by rounded, 
plateau-like tracts only slightly varied by shallow valleys. They are alike in form and origin 
but vary considerably in altitude, rising gradually toward the heads of the rivers, so that each 
main stream has its own particular set of altitudes. All of these basins, but the larger ones 
more conspicuously than the smaller ones, are now being dissected by the streams which drain 
them. In the case of the largest and most interesting of them all, the i\sheville basin, the main 
stream has intrenched itself well below its former level and the tributaries are intrenched by 
smaller amounts. The former plain has been carved into hills and valleys with thoroughly 
organized and graded waste slopes. But the dissection of the former plain has not yet reached 
the point where the earlier flatness can not be safely inferred, for some areas of flat land can still 

'The term "monadnock" is applied to a single isolated residual such as Mount Monad- 
nock in New Hampshire, which stands alone. More massive residuals of greater size and height 
would seem to require a different name, and the term "unaka" has been proposed for such 
large residuals as the Unaka Mountains which illustrate the type. 



6lO FOREST PHYSIOGRAPHY 

be made out here and there and the hilltops still reach accordant elevations, though the struc- 
ture and to a lesser degree the rock character vary from point to point. East of the Black 
Mountains, in the valley of the South Toe River, is a basin smaller than that of the French 
Broad at Asheville but made in a similar manner and now in process of dissection similar 
to that exhibited about Asheville, the river being intrenched about 200 or 300 feet below 
the general level of a comparatively even upland A third basin of this kind is that of the 
Caney River west of Mount Mitchell, but it is much smaller than the other two.i 

A topographic and drainage feature of the southern Appalachians 
that has a dominating influence in the distribution of the population 
and a direct relation to the growth and development of the forests is 
the distribution and character of the basins, gorges, and coves. The 
basins have already been defined in terms of topographic cycles and 
rock character as the result of local peneplanation of areas of more 
feldspathic rock. They vary in size from the many small, even tiny, 
fiat or gently rolling areas such as those found along the courses of the 
minor rivers to such large tracts as those on the Nolichucky and the 
Holston and the Asheville basin in the valley of the French Broad. 

Less important than the basins just described are the small plains 
that frequently occur at the headwaters of the streams. They are 
perched well up on the mountain slopes and reentrants, where the brooks 
or "branches" unite to form creeks. They appear upon irregular areas 
of softer rock, at stream junctions, and where land waste has been washed 
into the hollows of the mountain slopes. These basins are a common 
feature of the whole southern Appalachian mountain region. Between 
'the high coves and the basins at an intermediate level and also between 
the basins and the great valleys and plains that border the southern 
Appalachians the streams descend through gorges or steep valleys. Thus 
between the Asheville basin and the Great Appalachian Valley the French 
Broad leaves the wide valley in which it flows above Asheville and 
enters a gorge at Hot Springs, Tennessee; the Linnville flows through a 
broad valley above the falls at the Blue Ridge, then plunges down in a 
reversed curve to the quieter stretch of the Piedmont; to the same class 
belong the gorges of the New River above Ivanhoe, the Doe River above 
Elizabethtown, Tennessee, the Nolichucky above Unaka Springs, Ten- 
nessee, the Tallulah at Tallulah Falls, Georgia, and the Nantahala, 
Little Tennessee, and Hiwassee at the points where they make their 
steepest descents. In like manner the streams descend from the high- 
level coves to the level of the larger intermontane basins through gorges 
and canyons often rather steep-walled though seldom precipitous. 

1 For an interesting discussion of the Stream Contest along the Blue Ridge see a paper 
with that title by W. M. Davis, Bull. Geog. Soc. Phil., vol. 3, 1903, pp. 213-244. The paper 
also contains a short discussion of the general character of the southern Appalachians and 
the Piedmont Plateau. 



OLDER APPALACHIANS (SOUTHERN DIVISION) 



6ll 



In these two features of plains and gorges one has a large part of the 
physiography of the southern Appalachians that enters directly into 
relationship with man, for it is in the coves, basins, and plains that the 
350,000 people of the region are chiefly found and it is through these 
to a large extent that the development of the forest must proceed. 
Since the total area of the basin and valley lands is small, the popula- 
tion is small, and as scattered as the relatively flat lands they occupy. 
Only one-fourth of the tract is under cultivation of any kind, the wagon 
roads are chiefly ruts, and but one railway crosses the entire mountain 




Fig. 24s. — The uplifted and dissected local peneplain known as the Asheville Basin. 
(Keith, U. S. Geol. Surv.) 

region from east to west, though there are a score of feeders that enter 
it for considerable distances. It is largely to these features that the 
backward condition of the region is to be ascribed. Its life is but an 
eddy of the life of the surrounding plains; the mountaineer of the south- 
ern Appalachians is almost as crude as his somewhat more isolated 
brother in eastern Kentucky in what are locally known as the Kentucky 
Mountains. In both cases life is largely a struggle against space, 
whose vertical and horizontal elements are both discouragingly large. 

The succession of basins and gorges with falls and rapids is not ideal 
for the agricultural development of the southern Appalachians, but it 
has positive advantages for the mineral and forestry interests, since it 
affords an unrivaled source of energy. More than 6400 acres of land 



6l2 FOREST PHYSIOGRAPHY 

along the Blue Ridge, Unakas, and intermediate highlands have an 
elevation over 6000 feet, and about 54,000 acres are more than 5000 
feet above the sea. The Piedmont Plateau on the east is from 1000 to 
2000 feet high and the Great Appalachian Valley on the west" from 1500 
to 2000 feet high. Under these conditions the gradients of the streams 
are necessarily very steep; they fall from 2000 to 4000 feet within the 
mountains. It is estimated that about 1,000,000 horse power could 
be developed on the principal streams — the New, Kanawha, Holston, 
French Broad, Nolichucky, Little Tennessee, Coosa, Chattahoochee, 
Catawba, and a dozen others. At present water power is used in almost 
every settlement for grinding and sawing, and the larger towns are 
becoming to an increasing degree dependent upon it, but as a whole 
the greater part of this splendid resource is unused. 

In the development of the timber resources of the region two advan- 
tages are required that will not be long delayed — a denser population 
for labor supply and for markets. Already the manufacturing South 
is a reality. North Carolina cotton mills require more cotton than is 
grown in the state, those of South Carolina consume nearly three-fourths 
of the home-grown cotton,^ and the concentration of population to 
■ which these industries lead will greatly enlarge the demand for cheap 
lumber. At present some of the finest wood in the country is being sold 
for astonishingly low prices. For example, oak, cherry, walnut, and 
hickory commonly sell for $5 to $10 per thousand feet, and in scores 
of localities the difficulties of marketing the forest products limit the 
development of the timber to that required for local use.^ 

SOILS AND VEGETATION 

The soils of the southern Appalachians reflect the variations in rock 
character quite as faithfully as do the slopes of the mountains, the 
trends of the ranges, or the courses of the streams. Not only are the 
siliceous gneisses and the quartzites prominent topographically but they 
also have the thinnest soils; the feldspathic granites have the deepest 
soils and underlie the largest basins, as the Asheville basin in the valley 
of the French Broad. ^ The soils of the upper part of the Little Ten- 
nessee River basin are sandy, being derived from granite. On Little 
Tennessee River around and above Franklin most of the good farms 

1 E. R. Johnson, Sources of American Railway Freight Traffic, Bull. Am. Geog. Soc, vol. 
42, 1910, p. 246. 

2 Ayres and Ashe, The Southern Appalachian Forests, Prof. Paper U. S. Geol. Surv. No. 
37, 1905. 

3 Hall and Bolster, Surface Water Supply of the United States, Water-Supply Paper U. S. 
Geol. Surv. No. 243, 1910, p. 165. 



82 »/ 



,«^ ' 





SOUTHERX APPALACHIAN 

REGION 

LAMD CLASSIFICATION 

~J CLEARED 

1 MERCHANTABLE TIMBER 



4.io' 10 



Fig. 246. — The large cleared areas lie chiefly in local basins such as the AshevMe basin and the valley 
basins of the Little Tennessee. The smaller isolated areas are largely upon the hillslopes and in the 
upper and smaller basins or coves. 





Fig. 247. — Grassy "bald" andborderof spruce forest, White Top Mountain, Virginia. (U. S. Geol. Surv.) 

613 



6l4 FOREST PHYSIOGRAPHY 

are located on deep fertile red loams derived from schists. In the nar- 
row valleys among the high mountains, where sandstones, quartzite, 
and conglomerate prevail, the soils are generally thin and sandy and have 
little agricultural value; but on the north slopes and hollows, they bear 
well-developed forests. In the Hiwassee River basin deep valleys extend 
from the rivers far into the mountains between spurs five to twenty 
miles long. The mountain sides are steep and in many places rocky, 
while the creek valleys have considerable areas of alluvial flats and 
rolling foothills. The foothill soils are almost entirely clay and the 
alluvial flats along the river and creeks have a large percentage of clay. 
The soils of the mountain slopes are loamy and -moderately fertile; the 
ridges are covered with a light and stony soil that precludes agriculture.^ 

The distribution of the timber of the area is in general sympathetic 
with the major natural features. The principal timber is the oak of 
several varieties, found chiefly on the ridges, and the pines, found chiefly 
on the plains. The hemlock is found in strips or bands along the 
shaded ravines and on the better-watered northern or northwestern 
slopes between 3000 and 5000 feet. The northerly exposures also sup- 
port beech, maple, birch, etc. Shortleaf and pitch pine and hickory 
are found chiefly along the lower slopes of the Blue Ridge. Individual 
oaks reach their best development in the coves, though as a whole the 
stands are there too dense for the best reproduction. The soils of the 
ridge crests are generally too stony and thin for the best stands, though 
the conditions are very favorable for reproduction. Northerly expo- 
sures at the higher altitudes have the added dilflculty of being too cold, 
a condition that limits the productive power of the soils. Finally, on the 
higher summits of the Great Smoky, Pisgah, and Balsam mountains are 
a few thousand acres of black spruce occupying a habitat similar to 
that of the spruce forests of New England but very strictly limited in 
range because of the small proportion of land located at the requisite 
elevation for favorable conditions of temperature and humidity. 

The higher coves of the region have singular value and interest. In 
them the forest litter and leaf mold are generally thick, being washed 
down from the surrounding slopes. The soil of such localities is 
rarely ever wanting in humus, unless it has been recently reburned, as 
is sometimes the case with those coves located on the southern slopes, 
where there are less rainfall and a higher temperature and consequently 
more frequent and more destructive forest fires. 

Great havoc is being wrought in the region by the pursuit of cultural 

1 Hall and Bolster, Surface Water Supply of the United States, Water-Supply Paper U. S. 
Geol. Surv. No. 243, 1910, p. 190. 



OLDER APPALACHIANS (SOUTHERN DIVISION) 615 

and forestry methods which permit the too rapid wastage of the soils. 
At first the clearings were all located on the basin and valley floors, 
but as the population gradually increased and the old fields became 
depleted the clearings extended farther and farther up the valley sides be- 
yond the point where natural fertility is long maintained in the soil and 
where the land yields so poor a return that it ought always to remain 
in forest. As the cleared farms became unproductive the clearings were 
extended farther into the forest and the old fields allowed to revert to 
natural growth. Widespread erosion of hill and mountain slopes re- 
sulted, and great areas have in this way been rendered worthless, either 
through gullying or through the growing of useless brush. This is the 
rule within the mountain area, but along the western border of the 
Unakas and the eastern border of the Blue Ridge young quick-growing 
pines are the pioneers and cover the mountain slopes before gullying 
becomes too far advanced. Only the highest state of cultivation and 
the maintenance of brush dams and stone and earth terraces will pre- 
serve the soil upon the mountains and valley slopes once the natural 
forest cover is removed. So vigorous is erosion on the unprotected areas 
that the streams from them are often nearly half earth. Tending to the 
same destructive results is the overgrazing of considerable areas of the 
forest. As a result the young growth is checked or prevented altogether, 
the humus is depleted, the roots broken and bruised, and a rapid run- 
off ensues, which accumulates in effect and soon gains on the forest 
beyond the point of natural control. 

About 74% of the total area is still forested. Even this amount, 
however, is considered too small. Under the given conditions of slope 
gradient, soil texture, rainfall, etc., it is considered unsafe to have more 
than iS% to 20% of the surface cleared. Recent studies ^ have supplied 
clear-cut illustrations of soil erosion in a variety of situations: (i) on 
sodded "balds" where overgrazing and trampling by cattle have broken 
the turf and started landslides that quickly developed into gullies; 
(2) on all slopes where lumbering has removed the original protective 
covering and hastened the action of rain-wash; (3) on cleared and aban- 
doned slopes once used for agriculture. In the last-named case the harm 
has been underestimated in the past. Undercutting and caving, once 
started in a cleared area, often extend upward into forested tracts and 
the debris derived in this manner is washed downward into the forest 
below. Some porous soils are erosion-resisting but their aggregate area 
is not relatively great. The allowable limit of steepness for cleared lands, 

^ L. C. Glenn, Denudation and Erosion in the Southern Appalachian Region, Prof. Paper 
U. S. Geol. Surv. No. 62, igii, p. 137. Five plates, i fig. 



6l6 FOREST PHYSIOGRAPHY 

15°, is almost everywhere exceeded, and in many places greatly exceeded. 
Terracing is practiced on a wholly inadequate scale. There is increased 
silting on the flood plains and in the stream channels, a conclusion applied 
to all streams draining catchment areas that have been .extensively 
cleared. 

A great deal has been written concerning the evil effects of deforesta- 
tion upon soils and stream flow upon the assumption that the removal 
of a forest cover will inevitably and under all circumstances cause vigor- 
ous soil washing and floods. That some damage results upon the re- 
moval of a forest is axiomatic, but superlative terms can not be applied 
to all regions. Upon large areas of the sandy- plains of the northern 
part of the southern peninsula of Michigan the removal of the white- 
pine forests has indeed affected the regime of the streams to a large 
though not a disastrous degree; the sandy soil imbibes the rainfall as 
readily as forest litter and retains it, without washing, almost as effec- 
tively as the roots and ground litter of a forest. In general it may be 
said that the deforestation of a plains area with a sandy soil produces 
minimum effects upon stream flow. 

The vital feature of the forest physiography of a mountain region is 
the balance of power which the forest holds in the contest between 
soils and run-off. If in the run-off of a mountain region we grant any 
retarding effect at all, it follows that in those mountain regions in which 
the waste slopes are delicately organized and supply and demand sen- 
sitively balanced, the presence of the forest throws the advantage to the 
side of the soils and moderate and normal soil removal takes place at a 
rate compensated by the decay of the rock and soil formation. If on 
the other hand the forests be removed, their influence is withdrawn from 
the contest and run-off gains upon soil formation and disastrous soil 
wastage results. 

The primeval forests have a peculiarly sensitive relation to these proc- 
esses. In such regions the forest influence is expressed in the fashion- 
ing of the slopes, in the depth of decay of the rock, the rate of run-off, 
the amount of rain beating to which the soil is exposed, etc. Grant 
any degree of influence at all, however small, and the conclusion must 
follow that upon the removal of this influence — the forest — readjust- 
ment of relations must take place. The rain beats directly upon the 
soil, the retarding influence of the ground litter and tree roots and trunks 
is withdrawn, and more rapid soil removal occurs. 

When once these evil effects have been allowed to take place man- 
kind is deprived practically for thousands and even millions of years of 
the favorable conditions that preceded the epoch of destruction. In 



OLDER APPALACHIANS (SOUTHERN DIVISION) 617 




Fig. 248. — Protection against erosion by parallel ditches. (Ayres and Ashe, U. S. Gaol. Surv.) 



I'ig. 249. — Erosion checked by covering gulleys with brush, Longcreek, Va. (Ayres and rLsue, 

U. S. Gaol. Surv.) 



6i8 



FOREST PHYSIOGRAPHY 



a hundred years man may achieve such baneful results as nature will 
compensate only during a geologic period of hundreds of thousands of 
years. Soil is a resource of priceless value. On resistant rocks its forma- 
tion is excessively slow. The mills of the gods grind nowhere-with more 
exceeding slowness than here. Many glacial striae formed on resistant 
rock during the last glacial epoch, roughly 60,000 to 75,000 years ago, are 
still preserved as fresh as if they were made but yesterday. In that 
time man has come up from the cave and the stone hammer. Seventy 




Fig. 250. — Erosion checked by brush dams, Walnut Run, N. C. (Ayres and Ashe, U. S. Geol. Surv.) 

thousand years is a very short time for the development of a soil cover; 
for man it means a period so great that his mind can hardly appreciate 
it. The earth as we find it in the geologic to-day must be treated with 
care if the human race is to have a fair distribution of its wealth in 
time. To the geologic mind there is something shocking in the thought 
that a single lumber merchant may in 50 years deprive the human race 
of soil that required 10,000 years to form. 

These considerations apply with peculiar force to the southern Ap- 
palachians, which are in a subdued state of topographic development. 



OLDER APPALACHIANS (SOUTHERN DIVISION) 619 

Bare rock ledges are the exception; waste slopes are the rule. The eye 
may roam over hundreds and thousands of square miles of country and 
see only well-graded waste slopes, delicately organized waste removal. 
This means that rock decay has gained on soil removal, that the in- 
terior forces of the earth are relatively feeble, and that weathering has 
gained on uplift. In this interplay of forces the forests have had a 
prominent pa-rt and have contributed to the formation and holding in 
place of the soil cover, an effect reciprocally helpful to the forest. The 
forest cover removed, the waste slopes are dissected, soil removal gains 
on soil formation, and the effect is of such magnitude as to deserve the 
name ''geologic." Nor is the effect mitigated by systems of lakes such 
as occur in the glaciated mountains of the northern Appalachian region, 
the White and the Green mountains of New England. 

Lakes act as strainers and deprive the waters that flow from them of their cutting tools, 
so that erosion by lake-fed streams is generally far less vigorous than in the case of a lakeless 
land. A region of lakes is also commonly a glaciated region, and if the topography is mountain- 
ous the soil is often largely removed on the mountain slopes. It is patchy in distribution and 
alternates with areas of rock outcrop and ledge. Such a composition — lakes, clear streams, 
rock outcirops abundant, and soil patchy in development — means that the removal of the 
forest cover is not expressed in widespread denudation such as takes place under other con- 
ditions. 

Blue Ridge' 

The Blue Ridge, so-called, forms the eastern escarpment of the 
southern Appalachians and extends northward from their northern ex- 
tremity as far as. Pennsylvania. At the north it is a true ridge; at the 
south it is a great scarp that descends steeply from the upper level 
of the mountains to the lower level of the Piedmont Plateau. The 
gradients of the streams that flow eastward from it are excessively steep ; 
descents of 2000 feet are in many places made in 3 miles. So vigorous is 
the assault of these streams upon the divide between them and the long 
roundabout streams that flow westward to the Tennessee and the Mis- 
sissippi that the Blue Ridge divide is rapidly retreating westward. 

The Linnville River of western North Carolina has pushed its headwaters so far westward 
as to invade the valley of a stream flowing southwest to the Nohchucky. The valley side 
has been broken down and the feebler westward-flowing stream diverted to the Linnville and 
the Atlantic by a course about 2000 miles shorter than its former one. The profile of the 
Linnville shows a reversed curve at the point where it crosses the Blue Ridge, an indication 
that the capture has taken place so recently in a geologic sense that the gradient has not yet 
been worn down to normal form. In a good many other instances, as near Rutherford, North 
Carohna, where the South Fork of the New River is being endangered by Elk Creek, a head- 
water tributary of the Yadkin, capture of a similar sort is imminent, and, as the earth counts 
time, to-morrow will see similar diversions take place at these locahties. So strong is the con- 
trast between the gentler descents of the westward-flowing streams and the torrential descents 
of the eastward-flowing streams that steep headwater alcoves are often separated from well- 
developed meanders by only 2 or 3 miles, or less, of low divide. This great wall-like scarp has 



62 O FOREST PHYSIOGRAPHY 

been an effective barrier to the works of man, and only one railroad, that through the valley 
of the French Broad, via Asheville, crosses it. Elsewhere and in a large number of places the 
railroads run to the foot of the scarp, where they end abruptly. 

Eastward for several miles from the Blue Ridge escarpmeot, Fig. 251, 
the country is exceedingly broken and forms a wilderness of hills and long 
trailing spurs that enclose headwater coves where many rural popula- 
tion groups are found. Villages and individual farms are numerous, 
while the ''mountains" between the coves or the streams that head in 
the coves are wholly without inhabitants. To the people in the coves 
the Blue Ridge and the mountains beyond them are the "Land of the 
Sky." The escarpment is not a straight line -nor a straight wall but 
consists of a labyrinth of coves, hills, and spurs that represent strong 
differential erosion of a mass of highly irregular rock. Formerly the 




Fig. 251. — Plateau and escarpment of the Blue Ridge, looking southwest from Cassar's Head, S. C. 

(U. S. Geol. Surv.) 

highland west of the ridge extended much farther east, but the shorter 
eastward-flowing streams have been rapidly extending their headwaters 
westward since the uplift that followed or marked the close of the Cre- 
taceous cycle, and the spur and hill crests are but the reduced remnants 
of the eastern border of the upland. 

Typical spurs of this sort are Haines' Eyebrow and Singecat Ridge, and among the isolated 
hills a typical occurrence is Pilot Mountain, whose top is covered or protected by a remnant of 
quartzite from which fragments are constantly breaking off and cluttering the slopes and aid- 
ing in their resistance to erosion. 

North of the southern Appalachians the Blue Ridge changes its char- 
acter completely. In western Virginia and in its northern extensions 
in Maryland and south-central Pennsylvania it is a true ridge, but its 
topographic aspects are gentle and it is characterized by rounded spurs 
and knobs. It is soil covered throughout and bears forests, or culti- 
vated fields, or pastures, up to the summit. 



OLDER APPALACHIANS (SOUTHERN DIVISION) 



621 



The highest portion of the Blue Ridge north of North Carolina is about 05 miles south of 
the Potomac, where Stony Man and Hawk's Bill opposite Luray are 4031 and 4066 feet re- 
spectively above sea level. This is also the widest portion of the Blue Ridge, 10 to 16 miles. 
Northward the ridge crests are lower, and from Mount Marshall to the Potomac (50 miles) there 
are three deep gaps cut down to about 1000 feet — Snickers, .'Vshby, and Manassas gaps. South- 
ward from Mount Marshall (3150 feet) 100 miles to the James there are numerous smaller gaps, 
but they are all at higher elevations, about 2300 feet above the sea. 




Fig. 252. — Blue Ridge, Catoctin Mountain and Bull Run Mountain in Virginia. Blank areas represent 
Tertiary peneplain; shaded areas represent remnants of Cretaceous peneplain now appearing as 
residuals above the Tertiary level. (Keith, U. S. Geol. Surv.) 



62 2 



FOREST PHYSIOGRAPHY 



The Blue Ridge extends northward 
from the Potomac still as a quartz- 
ite ridge of rounded contour known 
as Catoctin Mountain in Maryland 
and finally into south-central Penn- 
sylvania near Carlisle, where it is 
known as South Mountain, reaching 
an elevation of 2000 feet, or about 
1000 to 1200 feet above the Cum- 
berland Valley which here borders it 
on the west. In New Jersey the 
Blue Ridge is represented by the 
highlands above Morristown, and 
the Highlands of the Hudson are 
really the northward continuation 
and expansion of the Blue Ridge. 
The latter form a narrow upland 
belt 1200 feet high and 12 miles wide 
that crosses the Hudson between 
Fishkill and Peekskill and continues 
east, merging finally with the upland 
of western New England. 

The Blue Ridge owes its ridge-like 
quahty in Virginia, Maryland, and 
south-central Pennsylvania to the 
harder rocks of which it is com- 
posed and to their superior resistance 
to erosion. These rocks are not 
everywhere uniform in character, 
and variations in altitude, breadth, 
and shape, of the Blue Ridge, occur 
in response to variations in rock 
character. Across Maryland and 
into Virginia as far as Berryville the 
Blue Ridge is formed upon resistant 
sandstones (Lower Cambrian), and 
over this portion its summit is rough 
and rocky and usually sharp- 
crested. South of Berryville the 
main crest is formed of an epidotic 
schist (Catoctin) and to some ex- 



P 



f 



OLDER APPALACHIANS (SOUTHERN DIVISION) 623 

tent of granite. The portion formed by the Catoctin schist is broad 
and has no very definite Unear arrangement, as shown on the map, Fig. 
252, so that the Blue Ridge through an expanse in breadth loses its sim- 
plicity and becomes markedly irregular in form. 

East of the Blue Ridge in western Virginia and central Maryland and parallel with it is a 
similar ridge of resistant material known as Catoctin Mountain and Bull Run Mountain, 
formed for the most part of hard sandstones (Lower Cambrian), with the exception of a 
small part of the southern end of Catoctin Mountain, where a schist (Catoctin) makes the 
summit of the range. Bull Run Mountain has crests developed upon resistant sandstone.' 

The structure of both Blue Ridge and Catoctin Mountain is synclinal, complicated by 
many faults; while the valley between them is anticlinal, and a similar structure is found in the 
Shenandoah Valley west of the Blue Ridge; so that while the Shenandoah Valley is at a lower 
elevation than the adjacent ridges, it is composed of younger rocks (Siluro-Cambrian hme- 
stone with occasional troughs of Lower Silurian shale). East of Catoctin Mountain the 
Piedmont Plateau is developed in the main on Newark strata composed of red sandstone and 
conglomerate. 

Piedmont Plateau 

The Piedmont Plateau extends southwestward from northern New 
Jersey and eastern Pennsylvania, its width gradually increasing from 
50 miles in Maryland to a maximum of about 125 miles in North Caro- 
lina. Beyond this point it narrows and in central Alabama finally 
passes beneath the sediments of the Coastal Plain. Its surface dips 
gently eastward at the rate of about 20 feet per mile from an altitude 
of 1000 to 1200 feet on the west to 400 or 500 on the east. 

The Piedmont Plateau is named from its position at the foot of the mountains that lie 
upon and beyond its western border. The name does not signify, however, that it has any of 
the characteristics of a piedmont alluvial plain, for its soils, topography, drainage, and physio- 
graphic development are in contrast to these features as developed on a foreland plain sub- 
ject to alluviation. 

The Piedmont province is a plateau only by reference to the low and 
flat Coastal Plain on the east, from which it rises by low bluffs or more 
strongly marked slopes than those developed upon the Coastal Plain. 
This border is marked by steepened stream descents and low falls and 
rapids. It is commonly designated the fall line, or fall zone. It prob- 
ably marks a simple monoclinal flexure or a series of slight faults whose 
down-throws are toward the east.^ The fall line is at variable distances 
from the coast; it is several hundred miles inland in Georgia and at the 
head of tidewater in the Chesapeake Bay region. Were the province 
otherwise situated it might never have received the name of plateau, 

1 A. Keith, Geology of the Catoctin Belt, 14th Ann. Rept. U. S. Geol. Surv., pt. 2, 1892-93, 
pp. 285-395- 

2 C. Abbe, Jr., A General Report on the Physiography of Maryland, Including the De- 
velopment of the Streams of the Piedmont Plateau, Maryland Weather Service, vol. i, pt. 2, 
pp. 115 et seq. 



624 FOREST PHYSIOGRAPHY 

for its absolute elevations are but little above those of the great plains 
of the earth. Indeed, as seen from the crest of the Blue Ridge (looking 
east) it appears as a low rolling plain. From the coastal side it appears 
essentially as an upland tract between a lower plains region and a 
region of mountainous relief. 

The western border of the Piedmont Plateau is more varied than 
its eastern border. On the south it extends to the outliers of, or to the 
foot of, the strongly developed eastward-facing escarpment of the Blue 
Ridge. The ascent to the higher province is here from looo to 2000 
feet in short distances. Northward the Blue Ridge becomes a true 
ridge and not only the eastern border of a mountainous country, a 
character which it retains as far as South Mountain, Pennsylvania. 
Farther north the whole Piedmont province changes in character as 
described in later paragraphs (p. 629). 

From any commanding point within the Piedmont Plateau the prov- 
ince appears not as a smooth plain but as a broadly undulating surface 
extending in every direction as far as the eye can reach; upon this gen- 
eral surface are low knobs and ridges rising above the general level of 
the plateau, while below the general level are numerous rather deep and 
narrow stream valleys and channels. The most striking feature of the 
piedmont topography is the even sky line formed by the rounded hill- 
tops which fall almost into a common plane that is not dependent upon 
or the result of the structural features of the region. The highly inclined 
and folded crystalline rocks of which it is chiefly composed and the 
softer Triassic sediments that occur in its central portion are both 
beveled off or truncated by the surface of the upland. It is inferred 
that the region has been subjected to long-continued and active erosion 
involving the reduction of lofty mountain ranges that once existed 
here. In this respect the Piedmont Plateau is but the seaward portion 
of a broad, gently rolling surface that once extended westward across 
the Blue Ridge, north along the Appalachians into New York and New- 
England, and south across the Cumberland Plateau of Tennessee. Since 
its development the surface of this lowland has been elevated and 
much dissected; the present higher mountain crests are the residuals 
which were never reduced to a lowland because of (a) their greater 
initial height, or (b) their greater hardness, or (c) their favorable position 
on stream divides, or {d) a combination of two or all of these conditions. 

The even contour of the surface of the Piedmont Plateau is not due 
to the underlying rock formations, for their structures are so diverse and 
complex as to produce a complex topography. The plain surface is due 
to peneplanation. An interesting survival of drainage conditions since 



OLDER APPALACHIANS (SOUTHERN DIVISION) 625 

peneplanation is shown in the courses of the larger streams, which are 
quite independent of the structure and character of the rock floor, while 
many of the tributary streams show adjustment to the character of the 
rock floor. The heterogeneity of the rock and the complexity of its 
structure are reflected in the indirect courses of the tributary streams 
and in the complex character of their valleys; but these structures are 
without expression in the case of the master streams. 

The Tertiary cycle of erosion in which the peneplain of the piedmont 
region was formed was closed by uplift and in consequence the gradients 
of all the streams were steepened and their erosive powers increased. 
Down-cutting was the immediate result, and since this has been ac- 
complished a certain amount of lateral swinging also has been accom- 
plished, so that many of the larger streams have limited flood plains and 
the smaller ones have graded waste slopes. The piedmont has been 
well dissected by the erosion of the present cycle, but dissection has not 
yet gone far enough to destroy the accordance of the hilltops, whose 
approach to a common altitude in a region of disordered rocks is 
the strongest evidence of the former existence of a base-leveled plain 
throughout the region. In harmony with this condition is the deeply 
weathered character of the rock which mantles all the hill slopes and 
even the hilltops, and under the influence of gravity and rain wash is 
slowly creeping down to the streams. 

So deeply decomposed was the rock of the Piedmont Plateau during 
the last stages of the long erosion cycle which resulted in its peneplana- 
tion that in spite of its later uplift and dissection many of the streams 
have not yet cut down to fresh rock.^ 

The middle and lower courses of the piedmont streams are gorge- 
like; the headwater tributaries commonly flow in broad shallow valleys 
separated by low rounded divides." With the gradual deepening and 
widening of the lower courses more marked dissection will take place 
along the headwater streams and their drainage basins will be roughened 
accordingly. 

The rocks of the Piedmont Plateau consist of a number of types each 
of which has had an important influence on the topography. They are 
chiefly crystalline and are derived in part from original sediments and 
in part from original igneous masses. They include crystalline gneisses 
and schists associated with crystalline limestones, quartzites, and phyl- 
lites intruded by granite, and a large variety of other types. 

1 L. C. Grafton, Reconnaissance of Some Gold and Tin Deposits of the Southern Appa- 
lachians, Bull. U. S. Geol. Surv. No. 2g3, 1006, p. 13. 

2 N. H. Darton, Washington Folio U. S. Geol. Surv. No. 70, 1901, p. i. 



626 FOREST PHYSIOGRAPHY 

The gneisses, granites, and gabbros all offer about the same resistance 
and form by far the greater part of the general surface of the plateau. 
They are developed in the form of rounded hills and gentle slopes 
on the upland surfaces. Bands of varying resistance are- distributed 
through these rocks, but they are very irregular in size and position and 
are therefore expressed in the topography by alternate softening and 
intensification of the contours of the valley walls and in expansions and 
contractions of the gorge floors. The phyllites, somewhat softer than the 
gneisses, form more rounded hills, gentler slopes, and valleys of broader 
proportions. Lenses of limestone and marble in the phyllite, with a 
high degree of solubility, have resulted in the development of broad 
flat-bottomed valleys. These limestone and marble bands are the 
weakest topographic factors among the piedmont rocks. 

The more resistant rocks and those most prominent topographically 
are serpentines, slates, quartz-schists, and quartzites, which stand out as 
ridges or rounded knolls above the surrounding gneiss. The serpentine 
is most striking topographically where it is crossed by streams; at such 
points, steep, bowlder-strewn, rocky gorges and rough channels have 
been developed. While the form and size of the piedmont valleys have 
a relation to the geologic structure, the courses of the streams on the 
whole have not been strongly influenced by the arrangement of the bed- 
rock, and this is true particularly among the larger streams, which flow 
markedly independent of the structure. 

TRIASSIC OF THE ATLANTIC SLOPE 

From the Minas Basin in the Bay of Fundy to the northern boundary 
of South Carolina there occurs at intervals a geologic formation of great 
physiographic importance, for its topography, soils, and vegetation are 
to a large degree exceptionally developed and are unlike the topography, 
soils, and vegetation of the bordering crystalline rock. The formation is 
of Triassic age and is commonly known as the Triassic formation of the 
Newark system of rocks, and occupies about 10,000 square miles of terri- 
tory. The general distribution of the formation is shown in Fig. 254, from 
which it will be observed that it does not occur as a continuous body of 
rock but as a series of elongated and detached areas occupying local 
basins of sedimentation. The longer axis of each area is roughly parallel 
to the main trend of the formation as a whole. There are in all thir- 
teen major areas besides a group of smaller areas. As a whole the belt 
is about 1200 miles long and always less than 100 miles wide. 

The principal rock members of the Newark system are sandstones, 
shales, and conglomerates, with local beds of slate and limestone and 



OLDER APPALACHIANS (SOUTHERN DIVISION) 



627 



a certain marginal development of arkose and breccia. Almost all the 
areas of Newark rocks have associated sheets and dikes of basic rock, 
chiefly basalt and diabase known under the collective name of trap. 
The dikes trend as a rule from northeast to southwest, cross indifferently 




»,T AY Lofevi 1?L-e' area 

DANVILLE^ f FrL'moX a're; 
ARE^ ;^/f^ c^^ '■ 



AREAS OCCUPIED 

BY THE 

NEWARK SYSTEM 

BASED ON 



100 



APS B¥ I.e. RUSSELL 

Scale 




■VaDESE'ORO AREA 



^ 






Fig. 254. — Local development of Triassic rock in the older Appalachians. The arrows indicate the direc- 
tion in which the strata dip. 

from sedimentaries to crystallines, and are narrower in the crystalline 
rocks bordering the area than they are in the sedimentary rock. 

In part the trap sheets are extrusive and in part intrusive. The trap of Nova Scotia is 
extrusive in origin; most of that in the Connecticut Valley is extrusive, with important intru- 
sives along West Rock Ridge and the Barndoor Hills north of the Ridge; along the eastern edge 
of the New Jersey Triassic are the Palisades, also of intrusive origin. In the Richmond and 
Catoctin areas the igneous rocks are of intrusive origin and usually occur in the form of sheets 
or sills, and dikes. 

The widespread occurrence of faults of all degrees of displacement 
from a few inches to several hundred feet has caused the repeated out- 
crop of individual strata. The faulting has almost everywhere resulted 
in either westward or eastward dips, roughly at right angles to the trend 
of the basins in which the formation lies. The larger faults are believed 



628 



FOREST PHYSIOGRAPHY 



to affect the underlying crystalline rock as well as the sandstone and 
the trap. 

In general the Triassic rocks have a monoclinal structure throughout 
and all have marginal faults; in some cases this is pronounced along one 



-'SPrr-.^.-Jni.-r.fj^.'JS^.^rTrr^r^ri^ 



Fig. 2SS. — Relations of the igneous rocks to the sedimentary strata (Newark) in New Jersey, Paterson 
quadrangle. Vertical scale three times the horizontal. True profile in lower section. (U. S. Geol. 
Surv.) 

border and in all cases it is developed to some degree. Some of the 
faults are large enough to bring to the surface the crystalline rock floor 
on which the sediments were deposited; others expose the basal con- 
glomerate; and still others expose only the lower trap sheets or the 




Fig. 256. ■ 



■ Palisades of the Hudson from the Jersey side, looking south. The vertical cliff of diabase and 
the sloping talus are characteristic. (U. S. Geol. Surv.) 



intermediate finer shales and sandstones. In addition to faults, broad 
undulations occur, but no true folds have been observed. The faults in 
many notable instances pass directly into the crystallines, where they 
produce marginal features of importance, although within the crystal- 



OLDER APPALACHIANS (SOUTHERN DIVISION) 629 

lines the structural and textural differences are not sufficiently marked 
to give rise to a type of topography as distinctive as that formed in 
the areas of Triassic rock where uniform structures prevail over wide 
areas and where strong and sudden alternations in hardness are the rule. 

The topographic expression of these belts of Triassic rock is not 
everywhere the same, but depends upon the nature of the surrounding 
country rock and the elevation. In the Connecticut Valley the Trias- 
sic rock rests upon and is bordered by crystalline rock which is very 
much harder than the sandstone. The elevation of the region above 
the sea is in the main from several hundred (near the sea) to 2000 feet 
and less (in the interior), and erosion has therefore been sufficiently 
active to degrade the soft rocks to a lowland, while making so little 
impression upon the hard rocks as to leave them in the form of uplands. 
On the other hand the Richmond basin of Virginia is a plain continu- 
ous with the plain developed upon the surrounding rock. In tli^s case 
it is not possible, except in a few localities, to infer any geologic change 
from a change in the topographic level, ^ a condition due not to the 
character of the surrounding rock, which is crystalline as in New England, 
but to the absence of pronounced elevation. The Richmond Triassic is 
on the eastern edge of the Piedmont Plateau and only a few hundred 
feet above sea level. 

The characteristic features of the Piedmont Plateau as developed in 
Georgia, South Carolina, etc., are modified to an important degree or 
wanting altogether over large portions of northern New Jersey, eastern 
Pennsylvania, and central Maryland, Virginia, and North Carolina be- 
cause of the occurrence of Triassic sandstone, the largest body of which 
occurs in New Jersey and Pennsylvania, Fig. 254. 

In New Jersey and Pennsylvania the Triassic is a gently rolling plain 
from 100 to 400 feet above the sea. It is lowest along its southeastern 
margin. The hills for the most part show a distinct northeast-southwest 
trend, which coincides with the strike of the underlying strata, and; in 
general reflects the slight variations in texture in the different sandstone 
layers. The relief is uniformly slight. Practically all the slopes are 
long and gentle and covered in most places with a thick, fertile soil. 
The general continuity of the plain is interrupted by valleys cut below 
the general level and by hills, ridges, and plateaus of harder rock that 
surmount the plain. The region was reduced to a peneplain during the 
Tertiary, and it is this that accounts for the general plain-like character 
of the region, but the reduction was only partial and the hard outcrops 

1 Shaler and Woodworth, Geology of the Richmond Basin, igth Ann. Rept. U. S. Geol. 
Surv., pt. 2, 1897-9S, p. 393. 



630 



FOREST PHYSIOGRAPHY 



of the included trap were in this cycle but little reduced below the level 
to which they were brought during the Jurassic-Cretaceous cycle of 
erosion. The crystalline rocks of the Piedmont are overlain and con- 
cealed by the Triassic sandstones and shales except, so to speak, on the 
four corners of the depression in which the Triassic rocks were de- 
posited. Here the crystallines run down into long tapering bodies of 




LEGEND 

Post-Newark l-'^'":-'1 

,, ( Sedimentary L__3 

'/NEWARK] „ „ , ^— 

' / Trap Rock ■■ 

Pre-New ark r - I 



Fig. 257. 



■The four crystalline prongs of the older Appalachuins which enclose the New York-Virginia 
area of Newark rocks. (Adapted from Russell, U. S. Geol. Surv.) 



rock upon which is developed a topography of a t3^e far different 
from that developed upon the Triassic strata. 

To these four narrow, tapering tracts the name prong has been 
applied by Professor Davis and each has been given a distinguishing 
name after the name of the town near its terminus. The prong that 
extends across southeastern Pennsylvania to Trenton is called the 
Trenton prong; the prong whose local name is South Mountain and 



OLDER APPALACHIANS (SOUTHERN DIVISION) 63 1 

which terminates near Carlisle, Pennsylvania, is the Carlisle prong; the 
narrow upland of crystalline rock which crosses northwestern New Jersey 
and terminates near Reading on the Schuylkill is the Reading prong; 
and the prong that includes and terminates Manhattan Island is called 
the Manhattan prong. Each prong has certain distinctive features 
which will now be described. 

The Highlands of New Jersey, the Reading prong, are made up of 
long, parallel, continuous ridges, separated by limestone valleys. 

"The side slopes are often steep and the soil on them is generally thin, rocky, and poor. 
Between the ridge hills lie secluded vales of rich farming lands, opened out on soft limestones, 
more or less hilly on a small scale, and directly comparable to the larger valleys of New Jersey. 
Similar valleys, though less numerous, are also found in other parts of the range, as Saucon 
Valley, occupied by the creek of the same name, and Oley Valley, near Reading." 1 

Toward the west the Reading prong consists of short, rounded, semi- 
detached hills, often stony and rugged, ranging roughly northeast and 
southwest. Although the hills over the greater part of the area are gen- 
erally rounded, the southern slopes are in most cases somewhat steeper, 
due to the inclination of hard strata at a high angle toward the south. 
The rather level summits of the highest hills reach a fairly uniform ele- 
vation between 900 and 1000 feet; occasional crests rising 100 or more 
feet higher represent residuals on the old peneplain surface of which all 
the summits were a part.^ 

The Carlisle prong (South Mountain, Penn.) extends south from op- 
posite Carlisle, in Cumberland County, has ia greater altitude and a 
more marked development of the ridge and valley type of surface than 
the Reading prong, and merges southward into the distinct single crest 
of the Blue Ridge. The general elevation is not less than 1000 feet 
throughout the range, though it increases toward the south, until along 
the Maryland line it reaches 2100 feet. As a result of greater elevation 
the hills toward the south appear less subdued than in the Reading 
prong, though there are no rocky peaks and few bare cliffs. The uni- 
formity of upland level is also less marked over the area in general 
than in the case of the Reading prong, though from a distance it presents 
a smooth, even sky line.^ The prong rises steeply from the sur- 
rounding valley plains and exposes a core of ancient volcanic rock and 
quartzite. The general structure is that of a broad uplift with minor 
folds on its surface which produce offsets of considerable magnitude. 

1 W. S. Tower, Regional and Economic Geography of Pennsylvania (Physiography), Bull. 
Geog. Soc. Phil., vol. 4, igo6, p. 21. 
^ Idem. 
3 Idem. 



632 



FOREST PHYSIOGRAPHY 



From its narrow northeastern extremity at the rapids of the Dela- 
ware just above Trenton, where the hills are Very low, the Trenton 
prong extends southwestward, widening gradually. The general eleva- 
tion of the upland level slowly rises from about 400 feet to 600 feet on the 
south, and the surface has an eastward slope to the Delaware River; the 
streams have cut many tortuous valleys and shallow ravines below the 
general level to depths of roo or 200 feet. The area may be described 
as a rolling country of rather even-topped hills and shallow dales. The 
hills are generally low. They are flat, to rounded or dome-shaped, with 
summits at a generally uniform level, expressive of the former base- 
leveling, and have gentle slopes coated with a thick layer of soil.^ 

The Manhattan prong descends from the level of the rugged uplands 
east and south of the Highlands of the Hudson to sea level at New 
York. The submergence of its outer border is marked and has made 
the lower Hudson a tidal estuary, broadened and deepened the East 
River, and given the coast an embayed character similar to that ex- 
hibited along the whole coast of New England. 




Fig. 258. — Terminal moraine and direction of ice movement in the vicinity of New York. 
(U. S. Geol. Surv.) 



1 W. S. Tower, Regional and Economic Geography of Pennsylvania (Physiography), Bull. 
Geog. Soc. Phil., vol. 4, 1906, p. ig. 



OLDER APPALACHIANS (SOUTHERN DIVISION) 



633 



In northern New Jersey lakes and ponds were formed in the glaciated 
belt by the irregular disposition of the glacial drift in such a manner as 
to make basins; while glaciation also gave rise to minor topographic 
features in marked contrast to those produced by erosion. The drift 
in northern New Jersey is thin, its average thickness being probably 
not over 15 feet, while the general relief is measured in terms of several 
hundred feet. Had the drift been disposed uniformly over the surface 
it would have had small effect on the topography. But in some 




Fig. 259. — Characteristic terminal-moraine topography. (U. S. Geol. Surv.) 

places the rock was left bare, while in others the drift was accumulated 
to a depth of scores of feet. In general the valleys received a heavier 
drift covering than the uplands, a covering which consists not only of 
glacial deposits themselves but of fluvio-glacial deposits related to 
them. The result of the filling of the valleys and the erosion of the 
intervalley ridges and uplands was to diminish the relief, though such 
diminution is nowhere marked.^ 



SOILS OF THE PIEDMONT PLATEAU ^ 

The soils of the extreme northern part of the Piedmont region, in 
New Jersey, are glacial, but elsewhere they are purely residual in origin, 
and have been derived almost exclusively from the weathering of igneous 
and metamorphic rocks. The chief exceptions are the detached areas of 
Triassic sandstones and shales. Marked differences in the character of 
the rock and in the methods of formation have given rise to a number 
of soil types, those derived from crystalline rocks being the most numer- 
ous and widely distributed. 

The most important and widely distributed soils of the Piedmont 
Plateau are known as the "red-clay lands" and are characterized by 
red clay subsoils, with gray to red soils ranging in texture from sand to 

1 R. D. Salisbury, The Physical Geography of New Jersey, Final Report of the Geol. 
Surv. of New Jersey, i8gs, pp. 155-156. 

2 Data chiefly from Soil Survey Field Book, U. S. Bur. Soils, 1906. 



634 FOREST PHYSIOGRAPHY 

clay, the lighter colors prevailing with the sandy members. The red- 
clay soils are of residual origin, derived from the degradation of igneous 
and metamorphic rocks which have been weathered generally to great 
depths, so that outcrops are rare. Fragments and bowlders of'the parent 
rocks are, however, found on the surface to a variable extent. 

An important type of red clay soils is a gravelly loam which has been 
derived from the breaking down of granites chiefly of a coarse-grained 
variety; it represents a less complete weathering of the rocks than some 
of the other types. The soil is a brown sandy loam about 7 inches 
deep, carrying variable quantities of feldspathic or quartz gravel. The 
subsoil is a heavy, micaceous, red loam or clay loam containing con- 
siderable gravel. Outcrops of granite appear in many places. A promi- 
nent feature of this type is a lack of tenacity in both soil and subsoil, 
as a result of which the land erodes and gullies in a serious manner. As 
a rule it occupies high broken uplands and the drainage is good. The 
characteristic timber growth is hickory, shortleaf pine, and some cedar. 

The fine sandy loam type of red sand soils is formed chiefly from the 
weathering of talcose schists and slates. It is light gray to pale yellow 
in color. Hickory, oak, and pine are the growths found on the better- 
drained areas, while gums are characteristic of its poorly drained phases. 
The Indian or purplish red soils derived from the weathering of red sand- 
stones and shales (Triassic) are developed in detached areas in shallow 
basins in the Piedmont from New England to South Carolina. 

The occurrence of a large number of fragments of shale (from 10% 
to 40%) in those soils derived from Triassic shales is characteristic, 
whence the local name "red gravel land" for the shale loams. The 
Triassic sandstones weather into gravelly and sandy loam types where 
they are coarse and into pure loams and silt loams where they are line. 
A stony loam type consists of very stony land, hilly to mountain- 
ous in character, generally covered with a natural forest of chestnut 
and oak. The soil consists of a rather heavy red loam, 8 to 10 inches 
deep, containing from 30% to 60% of red or brown sandstone frag- 
ments. The subsoil is of much the same character to a great depth. 
This type is derived from the more siliceous or hardened phase of the 
Triassic sandstone. It is well adapted to forestry and orcharding, and 
the more level areas, when the stones are removed, to general farm 
crops. 

The soils of residual origin, derived principally from mica schists, have 
yellow or only slightly reddish subsoils and gray or brown surface soils. 
They are also micaceous and subject to erosion. Locally they are, 
known as "gray lands," to distinguish them from the "red lands" de- 



OLDER APPALACHIANS (SOUTHERN DIVISION) 635 

rived from the Triassic sandstones. The topography is in general not so 
rough, being roIHng to moderately hilly. They are not deeply weathered, 
and the underlying rock is often encountered within 2 feet of the sur- 
face on slopes where erosion is pronounced and rarely more than 10 to 
15 feet below the surface. 

The gneisses and schists of Maryland, Pennsylvania, and Virginia 
weather into a stony loam containing from 30% to 60% of stony 
material. The type occurs on the summits of hills and ridges and on 
steep slopes where the drainage is good. 



CHAPTER XXX 

OLDER APPALACHIANS {Continued) 



NORTHERN OR NEW ENGLAND DIVISION 

The New England physiographic province is continuous with New 
Brunswick and Nova Scotia and that part of Quebec lying south of the 
St. Lawrence River. To a large degree it has shared in the physio- 
graphic history of these districts, the Laurentian Plateau of Canada, 
and the great Appalachian province of the United States of which it 
forms a large division. Like the adjacent regions a large part of 
the New England province was peneplaned (Jurassic and Cretaceous 
time), then uplifted, extensively dissected, and glaciated. In general 
terms it may be described as an upland, for it possesses a somewhat 
uniform upper surface which extends from an elevation of several hun- 
dred to two thousand feet above the sea. But this term can scarcely 
be applied to its outer margin. Recent depression has submerged the 
border of the region, and the upland character is not therefore con- 
spicuous on the immediate shore. The word upland or plateau, often 
applied to the New England province, also requires important modifi- 
cation when applied to certain interior portions of the New England 
region; for while most of the southern half of New England is accurately 
described as a dissected upland plain or plateau, the northern portion of 
New England bears important mountain groups, the White Mountains 
of New Hampshire, the Green Mountains of Vermont, and other 
groups of lesser height and size, besides a number of isolated mountain 
peaks such as Mount Katahdinnn central Maine and Mount Monad- 
nock in southern New Hampshire. Indeed, so mountainous are large 
parts of New Hampshire and Vermont that the mountain feature and 
not the plateau feature is conspicuous, and over large areas the plateau 
feature is not expressed at all. 

The western portions of Massachusetts and Connecticut are also more 
rugged than the central and eastern portions. The principal elevations 
are the Hoosac Mountains, the southern extension of the Green Moun- 
tains. Even in southern New England almost every general view em- 
braces one or more residuals of former lofty mountains. As elevations 
they are scarcely ever of notable scenic interest, though in a moderate 

636 



OLDER APPALACHIANS (NORTHERN DIVISION) 637 

way they are attractive with their forest-clad summits and slopes, 
drained by a large number of cool, spring-fed, torrential brooks. They 
are but the unimpressive remnants of a once more mountainous country. , 
In place of these trifling elevations were mountain peaks and ranges of 
alpine height bearing upon their flanks snow fields and perhaps glaciers. ■■ 

Upland Plain of New England 
The detailed topographic forms of the southern New England region 
have been carved in the Cretaceous peneplain since its elevation ; for 
this reason a knowledge of the peneplain feature is of great impor- 
tance in the study of the present topography. The argument for pene- 
planation is sustained by the striking accordance of level between 
different portions of the old peneplain developed alike on the crystalline 
rocks of the eastern and western uplands and the tilted lava sheets 
of the Triassic area of Massachusetts and Connecticut. Furthermore, 
no other process but peneplanation would give so uniform a slope to 
the surface southward toward Long Island Sound.^ An imaginary plane 
passed through the hill summits of the region would slope southeastward 
gently and would rest on nearly all the summits of both the eastern and 
western uplands. 

CRETACEOUS AND TERTIARY PENEPLAINS 

During the Jurassic and early Cretaceous periods the New England 
region, of rugged aspect because of displacements at the end of the 




■^ 



%~ CT3 




J) C 








(5 0) OCQ. 


,b' 


8 " ^■ 


,bO 




S ■§ >. 5 S; 


,0 


= e " >, 5^ 





OSqo «^ 


§;£• 



Fig. 260. — Profile across central New England, showing uplifted peneplain and the Mt. Monadnock 

residual. (Hitchcock.) 

1 Among the isolated residual elevations of New England Mount Monadnock in southern New 
Hampshire is typical. The name of the mountain is therefore applied to any isolated residual. 
Mount Monadnock rises 3866 feet above mean sea level and about 2000 feet above the sur- 
rounding plateau of southern New England. The peak does not stand alone, but is one of a 
family of monadnocks which includes Wachusett, Watatic, Asnebumskit, and others. All of 
them are believed to owe their survival to their position on the divides between the major 
streams rather than to the greater resistance of the rocks composing them. See J. H. Perry, 
Geology of Monadnock Mountain, New Hampshire, Jour. Geol., vol. 12, igo4, pp. 1-14. 

2 W. M. Davis, The Geological Dates of Origin of Certain Topographic Forms on the 
Atlantic Slope of the United States, Bull. Geol. See. Am., vol. 2, i8gi, p. 557. 



638 FOREST PHYSIOGRAPHY 

Triassic, was eroded practically to sea level. Topographic irregularities 
disappeared, hills melted under the forces of erosion until only their 
roots remained. A slight depression then occurred which submerged 
the outer border upon which were deposited Cretaceous se"diments of 
considerable depth and horizontal extent. At the beginning of the 
Tertiary period New England was again uplifted, but the uplift was 
of a broad regional variety. During uplift a slight tilt was given the 
land surface in the direction of the sea, so that the interior valleys 
were cut far below the general level. Dissection followed upon the 
uplift of early Tertiary time, the overlapping Cretaceous sediments of 
the southern border of the region were entirely removed, and the lime- 
stones of the Housatonic Valley, less resistant than the crystalline 
rocks in which they were enclosed, were reduced to a narrow lowland. 
The soft Triassic shales and sandstones of the Connecticut Valley were 
also worn down, forming a local peneplain bordered by crystalline 
uplands and surmounted by resistant trap ridges and hills. 

Again uplift occurred, which invigorated the streams and led not only 
to the deeper dissection of the remnants of the uplifted Cretaceous pene- 
plain but also to the dissection of the lower (Triassic) and more local 
lowland. The dissection of both the Cretaceous and Tertiary peneplains 
has everywhere brought into relief areas of softer and harder rock, even 
among the prevailingly hard crystallines where a relatively small degree 
of variability in resistance is the rule. Since the period of maximum 
uplift and dissection of southern New England there appears to have 
been a depression, for the outer border of the region is now drowned, as 
shown by the estuarine bays at the mouths of all the coastal streams 
and by Long Island Sound, which now occupies the inner lowland of 
the Coastal Plain, whose remnants are Long Island, Martha's Vineyard, 
Nantucket, and Cape Cod. 

Geologic Features 

The chief structural features of New England are (i) a western moun- 
tain axis extending through Vermont and western Massachusetts into 
Connecticut, (2) an eastern mountain axis extending through Maine and 
New Hampshire southward to the Sound, (3) a long, narrow, structural 
depression between these axes — the Connecticut Valley, and (4) two 
ancient basins on the eastern border of the province, the Boston and 
Narragansett basins. Each mountain axis is a line of topographic ele- 
vation on the north but has been worn to a lowland plain on the south, 
and, more recently, raised to form an upland. Since dissection ac- 
companied and followed uphft the plain has become a dissected upland. 



OLDER APPALACHIANS (NORTHERN DIVISION) 639 

Thus the Green Mountains extend through Vermont as a prominent 
mountain range but change from a range-like elevation to a plateau 
near the northern boundary of western Massachusetts. In a similar 
way the White Mountains terminate near the northern border of Massa- 
chusetts. The Connecticut Valley is everywhere a structural as well 
as a topographic depression, but it too has a northern and a southern 
section of unlike characteristics. On the common border of Vermont 
and New Hampshire it is a great synclinorium^ of crystalline Paleozoic 
rocks whose valley character has been emphasized by the predominance 
of rather easily denuded mica schists-; its southern continuation across 
Massachusetts and Connecticut is developed upon a block-faulted and 
much dissected mass of sandstones, shales, and conglomerates (Triassic) 
and intercalated trap sheets. 

The mountains and uplands east and west of the Connecticut Valley 
are composed mainly of crystalline rock — schists, gneisses, and granites 
of many varieties. In the western part of the province a considerable 
body of limestone occurs, a fact of physiographic importance since the 
limestones are characterized by topographic depressions and deep soils. 
The schists, gneisses, and granites are of variable composition and have 
been variously affected by the weather. The granite gneiss of Light- 
house Point, New Haven, is a very resistant rock and is but little 
weathered; the chlorite schist west of that city and on the eastern edge 
of the western upland is more deeply decayed, the planes of schistosity 
offering relatively easy means for the penetration of weathering agen- 
cies. In general the north-south trend of the structure is brought out 
rather clearly by the differences in resistance among the various rock 
types. The main valleys have been carved on north-south lines and 
the intervening ridges trend in the same direction. Railway construction 
on north-south lines is comparatively easy; construction on east-west 
lines is almost as difficult as in a mountainous country. 

Differences in rock character are largely responsible for differences in 
the valley widths in both the western and eastern uplands. The upper 
Housatonic and the Deerfield illustrate this relation admirably. The 
one flows southward in western Connecticut through a limestone belt 
and has developed a broad, deep valley of exceptional size; the other 
traverses a belt of resistant gneiss and its valley has a canyon-like 
aspect. The limestone is so soft relatively that good exposures of it 
are rare in individual stretches of a mile or more; many of the schist 

1 Pumpelly, Wolff, and Dale, Geology of the Green Mountains in Massachusetts, Mon. 
U. S. Geol. Surv., vol. 23, 1894. 

' C. H. Hitchcock, Geology of the Hanover Quadrangle, Kept. State Geol. Vt., 1905. 



640 FOREST PHYSIOGRAPHY 

and gneiss outcrops are so resistant that the striae of the glacial period 
are still clearly defined upon them. 

Effects or Glaciation 

TOPOGRAPHIC AND DRAINAGE MODIFICATIONS 

The last geologic event of topographic importance was the invasion 
of New England by the continental ice sheet which covered the north- 
ern portion of America. The ice removed the deep soils of the pene- 
plain from the interstream areas where they probably persisted even 
after preglacial uplift and dissection had removed large portions of 
them. The bed-rock was scoured and its weathered upper portion 
largely removed and fresh rock exposed. Rock ledges were commonly 
grooved, scratched, polished, and rounded by the land waste which 
clogged the lower portions of the ice, and minute irregularities of form 
and drainage were thus imposed upon the landscape. Glacial action 
produced a characteristic roughening of the surface, areas of soft rock 
were excavated to a greater depth than surrounding areas of hard rock, 
and reversed slopes were formed not only in the localities of glacial 
scour but also in those of glacial accumulation. A rearrangement of 
stream channels resulted in the filling of many depressions, and the 
formation of lakes and ponds and numberless falls and rapids. 

TILL DEPOSITS 

Of great interest in any glacial region is the distribution and extent of 
the glacial debris. New England was neither covered with heavy sheets 
of till as was the case with Illinois, Indiana, and other central-western 
states, nor so denuded of soils as Labrador and portions of New- 
foundland. Although rock outcrops are common and even abundant in 
southern New England, the sjirface consists in the main of a thin sheet 
of glacial material largely of local origin and of very complex compo- 
sition. A part of this material was brought into place by the glacial 
ice as subglacial drift, but the larger part is probably englacial material 
that was dropped in a confused and irregular manner upon the country 
as the ice sheet gradually melted away and disposed in large part re- 
gardless of the underlying topography. The lower few hundred feet of 
ice must have been heavily clogged with drift after the manner of the 
Greenland ice sheet to-day; and during the last stages of melting the stag- 
nant ice must have dropped its enclosed material upon the surface in 
the most irregular manner and largely without regard to the form of the 
surface upon which the ice rested. The relative absence of a drift cover 



OLDER APPALACHIANS (NORTHERN DIVISION) 641 

on the higher elevations, as on the trap ridges of the Connecticut Valley, 
is probably owing (i) to the greater freedom of the ice at this eleva- 
tion from drift, and (2) to postglacial erosion. The lower hilltops and 
many of the hill slopes bear quantities of glacial material. Hillside and 
hilltop farms are common, and their soils, when cleared of bowl- 
ders, are not sterile and easily impoverished, as is so often stated, but 
include some of the most naturally productive lands of the region. 
Their chief defects are an excessive amount of bowlders and a tendency 
to erosion when kept cleared of the native vegetation. Locally there 
exist extensive areas of glacial till, as in Aroostook County, Maine, and 
in all the valley lowlands, especially the Connecticut Valley lowland. 
Such areas are as a rule intensively farmed, whether they are of large 
or of small extent. They and the drained swamps and valley floors of 
the coastal regions represent the chief basis of the agricultural inter- 
ests of New England. 

The more rugged northern portion of New England bears a smaller 
quantity of glacially derived land waste. Its more northerly position 
subjected it to more intense erosion because the southward-flowing ice 
was there thicker and hence more powerful, while the greater relief of 
the section gave abundant opportunity for the thorough scouring of the 
more exposed and higher masses against which the ice impinged. Its 
hilltops and sides are bare or the rock is thinly veiled with a bowldery 
till. The most notable accumulations of material are in the valleys and 
especially at the point of convergence of several valleys where en- 
glacial material, often in large amounts, was dropped at the time of the 
disappearance of the continental ice sheet. 

ESKERS, DELTA PLAINS, AND SAND PLAINS 

Eskers occur in greatest abundance in southern Maine, where they 
were formed during the waning stages of the glacial invasion. They 
represent channel deposits of subglacial and englacial streams that dis- 
charged across the zone of wastage of the continental ice sheet. They 
form a not inconsiderable part of the total area and are conspicuous re- 
lief features, often extending for a score of miles without a break of any 
sort and with even summits, again crossing hills and valleys, the level 
undulating in sympathy with the general topography. Their compo- 
sition is rather uniformly of sand, gravel, and stones of medium size, 
the whole with various degrees of stratification but always somewhat 
sorted. Their slopes are commonly so steep as to be uncultivated and 
wooded. The tops are so narrow that although flat they are not of 
suflBicient area to make cultivation worth while. In the other New 



642 FOREST PHYSIOGRAPHY 

England states they are found here and there, but they do not generally 
form important elements of the rehef nor have that great length that 
marks the eskers of Maine. 

In a fiat region glacial sand plains are often inconspicuous topo- 
graphic features, but in so rough a country as New England every flat 
tract, be it sand plain, salt marsh, or valley floor, introduces into the 
landscape an unusual element that catches the eye and enhances the 
view. The general roughness of the surface of New England is respon- 
sible for the formation of a large number of sand plains, glacial deltas, 
and allied forms that are important topographic features. During the 
period of deglaciation a large number of small- water bodies developed 
in front of the ice as the ice impounded the drainage of some local 
basin draining toward it, and into these water bodies streams were dis- 
charged and deltas were accumulated. Later drainage of such lakes 
by the disappearance of the ice exposed the deltas and allowed their 
dissection. 

Where alluvial material was accumulated in front of the- ice and not 
in a body of standing water it commonly formed a sand plain or valley 
train, the one if deposition took place upon a rather flat plain, the 
other if deposition took place in a narrow valley. Locally sand plains 
are sometimes found along the borders of valleys where deposition took 
place at the mouth of some tributary while the main valley was still 
filled with ice. Such plains are commonly associated with rude ter- 
races of which they themselves form a part. The terraced effect was 
gained by the disappearance of the ice, which left the outer edge of the 
accumulated material unsupported. 

STREAM TERRACES 

The influence of glaciation is also expressed in stream terraces built 
during a period of stream aggradation associated with the retreat of 
the ice. It now seems probable that aggradation was enforced as much 
by the lower gradient of the valleys during the waning of the ice sheet 
as by the abundance of land waste contributed to them. In this view 
the change from aggradation to that degradation which resulted in the 
terracing of the aggraded material was invoked by both decreased waste 
supply and tilting of the land. The tilting is common in a very large 
region including at least the Great Lake district. New England, and 
the Laurentian Plateau. 

The Connecticut and Merrimac valleys on the New Hampshire 
boundary have been to some extent mapped and leveled and the ter- 
races identified. The highest terraces and deltas of tributaries rep- 



OLDER APPALACHIANS (NORTHERN DIVISION) 643 

resent the remnants of an ancient flood plain; they stand quite uni- 
formly about 200 feet above the Connecticut River, except where a 
tributary enters.^ 

Farther south the attitude of the Connecticut Valley was such as to 
favor the formation of a succession of lakes. There were three main 
bodies of water — Montague, Hadley, and Springfield lakes — sepa- 
rated from each other by the central trap ridges. Tributaries accu- 
mulated sand and gi^avel deltas on the lake margin, fine laminated clays 
(in which arctic leaves have been found) were spread over the lake 
floors, and shore lines were formed. On the northern border of Mas- 
sachusetts these accumulations are now 380 feet above the sea, at 
Northampton they are at 300 feet, on the southern border of the state 
they are at 180 feet, and at New Haven correlative deposits are near 
sea level. The southward tilting of the land which these southward- 
diminishing elevations imply, drained the lakes, gave the Connecticut 
greater erosive power, and resulted in the formation of the great terraces 
that now border that stream and enhance its scenery as well as the 
productivity of the valley.^ 

While the New England terraces are everywhere the product of 
either the tilting of the land or decreased waste supply or both, their 
disposition, size, and field relations offer a great variety of conditions. 
In the Connecticut Valley they seem in the main to have been con- 
trolled in their size and shape by natural unrestrained meander growth 
and stream deflection. In the Westfield Valley, and presumably in a 
large number of others not yet examined, their development appears to 
be guided largely by the rock sides of the preglacial valley.^ 

LAKES 

Lakes are among the most characteristic features of a glaciated sur- 
face and are of special interest in connection with forests and stream 
flow. They are very abundant in New England, Connecticut alone 
including more than 1000, and together with swamps and marshes they 
occupy 145 square miles, or about 3% of the surface of that state. In 
Maine the proportion of surface occupied by lake is greater than in any 
other state in New England; 5% to 10% of the total area of the larger 
catchment basins is the rule. The lakes have a very beneficial effect 
upon both the climate and the run-off. They act as great reservoirs, and 
though they rise and fall with the seasons, they do so over larger areas 

1 C. H. Hitchcock, The Geology of New Hampshire, Jour. Geol., vol. 4, 1896, p. 61. 

2 B. K. Emerson, Holyoke Folio U. S. Geol. Surv. No. 50, 1898, p. 3, col. 4. 

' W. M. Davis, River Terraces in New England, Bull. Mus. Comp. Zool., vol. 38, 1902, 
pp. 281-346. 



644 FOREST PHYSIOGRAPHY 

than the rivers and therefore by smaller vertical amounts. They 
steady the river discharges by holding large volumes of water but little 
above the level of the outlet both in time of flood and in time of drought. 
It is perhaps the general conception that of two groups 'of streams 
occurring in regions of equal rainfall and comparable relief, that group 
that has the larger number of lakes will have the more even flow 
through the year. In this view the rivers of New England should have 
fluctuations of lesser value than the lakeless streams of the broken por- 
tions of the Middle Atlantic States. To test this generalization the 
author made some computations of the average discharge of 30 New 
England streams from the St. John to the Connecticut during the 
months of May and November, 1908, the months which appear by 
rough estimation to represent the greatest departures in opposite direc- 
tions from the normal discharge for 1908.^ It was found that the 
ratio of discharge in the month (November) showing least discharge to 
the month (May) showing the greatest discharge is i : 11.6. Similar 
computations for the 14 streams between the Susquehanna and the 
Rappahannock, almost wholly outside the glaciated area and the region 
of the lakes, is i : 7. The influence of the lakes would seem theoreti- 
cally to throw these ratios in the other direction. The cause for this 
curious condition is probably found in the facts (i) that the northern 
streams are fed by the rapidly melting snows of spring, the discharge 
lagging behind the time of maximum melting, and (2) that the thinner 
soil of New England enforces a more rapid run-off. 

A partial test of this explanation would be the examination of two stream systems in the 
glaciated area, one in the region of no snow or of early melting snows and the other in the 
region of late snows. 

Were it not for the lakes the fluctuations of stream discharge would be still greater in the 
lake region than they now are, for the effect of the rapid melting of the snows would not then 
be mitigated. A thorough test of this conclusion would require an examination of streams 
throughout whose catchment are& the forest cover is in the same state of preservation and 
the topography is of the same quality but whose drainage systems contained widely different 
percentages of lake basin. A partial test is the contrast afforded by the St. Croix and the 
Penobscot. The St. Croix basin is well covered with forest, the Penobscot is about two-thirds 
covered with forest; the former has about io% of lake and pond surface, the latter about 6%. 
In harmony with these figures are the ratios of discharge for May and November, 1908, which 
are i : 5 for the St. Croix and i : 8 for the Penobscot. The Merrimac basin has about 3.6% of 
lake and pond surface, and the ratios of discharge for May and November are also i : 8 respec- 
tively for this river. 

These figures clearly show the influence of the lakes in retarding the 
flow and also how disastrous the floods of New England would be if 

> The basis of these computations is the summary table by Barrows and Bolster, The 
Surface Water Supply of the United States, 1907-8, pt. I, North Atlantic Coast, Water- 
Supply Paper No. 241, 1910, pp. 342-344. 



OLDER APPALACHIANS (NORTHERN DIVISION) 645 

the lakes did not exist. Though New England is a lake country, its 
forests are needed to help equalize stream flow to an even greater degree 
than more rugged southern districts where snows are absent or light or 
melt at more regular intervals and where the soils are deep. 

SUBREGIONS OF THE NeW ENGLAND PROVINCE 

Having examined the general physiographic features of the New 
England province we shall now consider the special features of the topog- 
raphy, drainage, and soil of a number of exceptional subregions. 

The largest of these subregions are: 

(i) White Mountains and bordering uplands. 

(2) Green Mountains and bordering uplands. 

(3) Connecticut Valley lowland and associated trap ridges. 

White Mountains and Bordering Uplands 

The most interesting and important mountains in New England are 
the White Mountains of New Hampshire. Their highest summit, 
Mount Washington, is 6290 feet above the sea and is the nearest New 
England rival of Mount Mitchell, N. C. (6711 feet), the highest peak 
in the eastern part of the United States. The most important single 
feature of the White Mountains is the Presidential Range, which be- 
sides Mount Washington includes Mount Jefferson, 5725 feet. Mount 
Adams, 5805 feet. Mount Madison, 5380 feet. Mount Monroe, 5390 
feet, and a number of other peaks of comparable altitude. This range 
extends roughly north and south, which is the prevailing trend of the 
other ranges that constitute the group, although there are many de- 
partures in detail from the general condition, such as the northeast 
trend of the Dartmouth Range, the northwest trend of the Belknap 
Range, the great curve from east-west to north-south in the Randolph 
Range, etc. The valleys about and among the White Mountains lie at 
elevations ranging from 500 to 1000 feet, and the plateau remnants that 
lie about their bases are from 1000 to 2000 feet above the sea. Their 
relative elevations are therefore but little less than their absolute eleva- 
tions and their influence as cloud gatherers and rain condensers is con- 
spicuous. The average precipitation of the mountains is perhaps from 
10 to 15 inches more than that of the surrounding valleys and plateaus, 
although no accurate observations of this condition for a period of 
years have yet been made.^ 

1 For incomplete data as to the rainfall and the snowfall of the White Mountains consult 
A. J. Henry, Climatology of the United States, U. S. Weather Bureau, Bull. Q, 1906, p. 120; and 
S. A. Nelson, The Meteorology of Mount Washington, Geological Survey of New Hampshire, 
1871; Water-Supply Paper U. S. Geol. Surv. No. 234, 1909, pp. 7-76 et al, map, Plate i. 



646 FOREST PHYSIOGRAPHY 

The White Mountains constitute the most important part of the 
eastern mountain axis in New England, which has two points of differ- 
ence when compared with the western or Green Mountains axis: (i) it 
is composed largely of igneous rocks while the western range consists 
largely of metamorphic rocks, and (2) it has no southern representative 
in the Older Appalachians. Like the western range the eastern is bor- 
dered on one side by sedimentary rocks; the Carboniferous conglom- 
erates, sandstones, and shales of the Boston and Narragansett basins 
lie on the eastern flanks of the New Hampshire-Maine axis, just as 
limestones, sandstones, and grits lie on the western flanks of the Green 
Mountains axis. The geosynclinal structure combined with the lesser 
resistance of the basin sediments as compared with the bordering igneous 
rocks have resulted in the development of lowlands, and the drowning 
of portions of the lowlands thus developed has given rise to Boston Bay 
and Narragansett Bay. 

The eastern mountain axis of New England extends northward and 
northeastward through New Hampshire and northern Maine where it 
forms a belt of rough country, Plate V. Mount Katahdin, Maine, is a 
part of the White Mountain district. The White Mountains are the only 
part of this mountain axis that have not been reduced to a lowland, then 
uplifted, dissected, and glaciated. Elsewhere the surface has been so 
completely base-leveled that only isolated residuals occur, such as Mount 
Katahdin in Maine, Mount Monadnock in New Hampshire, Mount 
Wachusett in Massachusetts, and other monadnocks of less importance. 

The whole of Maine southeastward of the White Mountains axis is 
a gently inclined upland sloping with marked regularity toward the sea. 
The degree of base-leveling which it reached at the end of a previous 



m^ 



Fig. 261. — Section south of Blue Hill, Maine, showing the base-leveled surface of the uplands bordering 
the White Mountains on the east. 2, granite; 3, diorite, diabase, and gabbro; 4, schist. (Emmons, 
U. S. Geol. Surv.) 

erosion cycle is indicated in Fig. 261. It must of course be remembered 
that isolated unreduced masses occur even here where the general reduc- 
tion of the rough topography appropriate to a disordered mass of rock 
such as the figure indicates is so complete. Mount Desert Island is per- 
haps the best-known residual of this sort. Its highest peaks are but 
little over 1000 feet above the sea. 

In so far as the geology of the White Mountains has been deciphered 
there is warrant for the conclusion that the general structure of the 



OLDER APPALACHIANS (NORTHERN DIVISION) 647 

main or Presidential Range is that of a great overturned anticline.^ 
The subsidiary ranges are in general also anticlinal, while the main 
valleys or depressions are considered as synclinal in structure. If these 
interpretations are correct, the White Mountains as a whole may be 
described as a geanticline or an anticlinorium.^ 

The general mountainous condition in so far as it depends upon ele- 
vation may then be assigned to uplift of the rocks of the White Moun- 
tains in the form of an anticlinorium; this is to be regarded as the net 
result of a long series of very complex mountain-making movements. 
During the long erosion interval which in southern New England produced 
a peneplain, the White Mountains were worn lower than previously but 
not completely reduced. The White Mountains of to-day should there- 
fore be regarded as but the remnants of far higher mountains worn down 
to moderate elevation. With the uplift of the peneplain in late Creta- 
ceous and early and late Tertiary times the White Mountains were also 
broadly uplifted, and from the gradual rise of the peneplain in their direc- 
tion we may reasonably infer that the uplift was more pronounced in 
the mountain belt than elsewhere. It may have amounted to 2000 
feet. 

Following uplift, vigorous erosion set in, with the result that the profiles 
were steepened and the relief developed on bolder lines than before. 
Still further variety was given the relief by glacial action. It is note- 
worthy that in general the relief is steeper along the main lines of gla- 
cial flow, as if from more pronounced scour of the preglacial valley 
borders. The combined effects of preglacial and glacial scour and erosion 
were the fashioning of the slopes on bolder lines, so that the relief at 
times becomes almost alpine. The degree of steepness is suggested by 
the destructive landslides that have occurred in the past and may occur 
in places again.^ 

Details of slopes in the White Mountains are as complicated as the 
structure upon which in most cases they have a certain dependence. 
General statements are of little value in this connection. The wedge- 
shaped mass of granite in the White Mountain Notch is more easily 
weathered than the flinty rock of anticlinal structure and high dip in 
Mount Willey and Mount Webster on either side, so that it has been 
excavated as a deep valley bordered by excessively steep walls, and is 
one of the most notable scenic features of the region. Granite seems 

1 C. H. Hitchcock, Geological Survey of New Hampshire, 1871, p. 8; also the same author's 
Geology of the White Mountains, Appalachia, vol. i, 1879, pp. 72-74. 

2 For definition see Chamberlain and Salisbury, Geology, vol. i, p. 485. 

» C. H. Hitchcock, The Recent Landslide in the White Mountains, Science, vol. 6, 1885, 
pp. 84-87. 



648 FOREST PHYSIOGRAPHY 

everywhere to be the least resistant rock and to underiie the valleys.^ 
Where it occurs as a narrow band the valleys are steep-sided, being 
bordered by more resistant schists, etc.; where it occurs in broad bands 
the valleys are wide. 

During the closing stages (Champlain) of glaciation a climate suffi- 
ciently Arctic existed, to produce local glaciers upon the Laurentides 
and the Green and the White mountains.- From each central mer de 
glace alpine glaciers moved radially outward, into the intermediate 
tracts which may have been submerged.^ The detailed occurrence 
of transported bowlders and lateral and terminal moraines upon which 
these conclusions rest is indicated in the two last-named references. In 
one stretch of about two miles north of Bethlehem village sixteen terminal 
moraines have been identified. 

Agassiz notes that the number of the moraines is here greater than in the case of a spot 
long regarded as particularly favorable for such phenomena, the valley of the Rhone below the 
Rhone glacier; and he believes that no one who had studied similar phenomena in connection 
with living glaciers could doubt the glacial explanation of these forms. Besides these evidences 
there have been found by numerous observers glacial cirques of subperfect development 
which must be assigned to the action of local glaciers such as those that have occurred in the 
Mount Toby district, Massachusetts, and on Mount Katahdin, Maine. The chief valleys affected 
by the local glaciers, which in one instance attained a length of 12 miles, are the Peabody, 
Ellis, Saco, Ammonoosuc, Pemigewasset, and others. With the removal of the mountain 
forests and the more detailed observations of the topography which this makes possible, many 
more evidences of a similar nature will probably be found. 

Green Mountains and Bordering Uplands 

Vermont, the Green Mountain State, contains the largest portion of the 
Green Mountains, which extend across it from north to south as a rugged 
chain of ridges and hills. Save for the alluvial terraces and patches of 
till on the western border of the Connecticut Valley, and for the so-called 
valley of Vermont on the western border of the state, there is little arable 
land. The total length of the Green Mountains is about 250 miles; their 
width varies from 25 to 50 miles. The range extends from central- 
western Connecticut through western Massachusetts, northward across 
Vermont, then turns northeastward, and terminates in eastern Quebec 
and northern New Brunswick on the southern border of the St. Lawrence 

> C. H. Hitchcock, The Geology and Topography of the White Mountains, Am.. Nat., vol. 4, 
1871, p. 568. 

2 A. S. Packard, Evidences of the Existence of Ancient Local Glaciers in the White Moun- 
tain Valleys, Am. Jour. Sci., 2d ser., vol. 43, 1867, pp. 42-43; Louis Agassiz, The Former 
Existence of Local Glaciers in the White Mountains, Am. Nat., vol. 4, 1871, pp. 550-558; 
C. H. Hitchcock, Glacial Markings among the White Mountains, Appalachia, vol. i, 1879, 
pp. 243-246. 

3 C. H. Hitchcock, The Geology of New Hampshire, Jour. Geol., vol. 4, 1896, pp. 60-62. 



OLDER APPALACHIANS (NORTHERN DIVISION) 649 

Valley in Quebec near the meridian of 70° west longitude. The northern 
termination has a strong northeastward trend parallel with the border- 
ing St. Lawrence Valley. 

The Green Mountains are the northernmost representatives of the 
mountainous western border of the older Appalachians and correspond 
in position with the Great Smokies of western North Carolina, South 
Mountain, Pennsylvania, and the Highlands of New Jersey. The axis 
as developed in the United States consists of three distinctly unlike 
parts: (i) a northern, discontinuous section, (2) a continuous range 
section extending through the southern two-thirds of Vermont, (3) a 
plateau section in western Connecticut and Massachusetts. 

The northern section of the Green Mountains in the United States 
contains the highest peaks of the range and might therefore be thought 
the most rugged and difficult to cross. On the contrary, four valleys 
cross it, and dissection along them has been so pronounced that roads 
are obliged to ascend to an elevation of only 500 feet. 

The four valleys, named in order from north to south, are: the St. Francis, in Canada; the 
Missisico, near the international boundary; the Lamoille, near Mount Mansfield; and the Wi- 
nooski at Bolton; and in them all the drainage is from the eastern border of the mountains 
toward the west and northwest, unlike the drainage of the southern end of the Green Mountains 
axis, which is from the western border eastward. The highest peak in the Green Mountains is 
Mount Mansfield, 4430 feet, and Mount Killington is but a little less at 4380 feet.' 

The second section of the Green Mountains extends from Hoosac 
Mountain northward for about 100 miles with an absence of passes and 
considerable uniformity of summit level, so that roads crossing this 
section not infrequently rise to an altitude of 2000 feet above the sea. 
The highest peaks of this section are under 4000 feet high and in general 
range between 2500 and 3500, with the larger number reaching to a little 
over 3000 feet. 

In Vermont the main axis of the Green Mountains consists of a series 
of sharply compressed folds striking approximately north and south in 
sympathy with the general trend of the range. The series is over- 
turned to the west in most localities. Steep westerly slopes are char- 
acteristic and occur in the form of terrace scarps on a large scale or as 
mountain brows of precipitous quality. The eastern slopes are char- 
acteristically formed on the dip of the planes of the schistosity or the 
dip of the planes of stratification and are steep or gentle as the dips 
vary between these extremes, although in general they may be called 

1 C. H. Hitchcock, Glaciation of the Green Mountain Range, Rept. of the State Geologist 
of Vermont, 1904, pp. 69-71; A. D. Hager, Physical Geography and Scenery, Geology of Ver- 
mont, pt. 2, 1862, pp. 144-145. 



650 FOREST PHYSIOGRAPHY 

relatively gentle. West of the Green Mountain range is a great lime- 
stone valley with island-Hke ridges of folded schist with synclinal struc- 
ture, the remnants of former more extensive formations largely removed 
by erosion.^ 

That portion of the Green Mountains in the northwestern corner of 
Massachusetts and near the Vermont boundary is called the Hoosac 
Mountains and forms the divide between the Hoosac and Deerfield 
rivers, branches of the Hudson and the Connecticut respectively.^ 

The Green Mountains extend into Massachusetts and Connecticut, 
but their form undergoes a radical change south of Hoosac Mountain, 
Massachusetts, where they are developed as a broad plateau extending 
from the Connecticut Valley on the east to the upper valleys of the 
Hoosic and Housatonic rivers on the western border of Massachusetts 
and Connecticut. Its western border is a bold continuous scarp 
about 2000 feet high, which forms the eastern border of the Berk- 
shire Hills country and is a divide between the tributaries of the 
Connecticut and the Housatonic; eastward the plateau descends by a 
more gradual and undulating slope as far as the western border of the 
Connecticut Valley lowland, where it descends from the 1000- foot level 
to the 400-foot level of the lowland floor in distances of a half mile to 
a mile. 

The Green Mountains of western Massachusetts and northwestern 
Connecticut (the Green Mountain Plateau) are mountains of the 
second generation. Their original mountain forms were obliterated by 
the peneplanation which affected the region in Jurassic and Cretaceous 
times. Whatever of mountain form they possess to-day has been de- 
rived by uplift and erosion since peneplanation. Occasional residuals 
rising above the ancient peneplain as low eminences are now the 
highest points of the region, affording fine panoramas over a broad ex- 
panse of upland. 

The Tertiary lowlands developed upon the softer limestones of western Connecticut and 
Massachusetts and the sandstones of the Connecticut Valley establish a surface which is of flatter 
gradient than the surface of the Green Mountain Plateau (a portion of the old Cretaceous 
peneplain) and appears to indicate that the uplift of the region after peneplanation was not 
uniform throughout but that it was somewhat sharply localized along the old mountain axis, 
after the manner of the uplifts that have been determined in the southern Appalachians 
(P- 393). When this is combined with the fact that most of the residual elevations on the 
divide between the Connecticut and the Housatonic lie upon the Green Mountains axis it 
will be readily understood that dissection since uplift has acted with unusual vigor here and 
given the region a rugged and mountainous appearance. 

1 Pumpelly, Wolff, and Dale, Geology of the Green Mountains in Massachusetts, Moa 
U. S. Geol. Surv., vol. 23, 1894. 

2 Idem. 



OLDER APPALACHIANS (NORTHERN DIVISION) 65 1 

Between the Green Mountains axis in western Connecticut, Massa- 
chusetts, and Vermont on the one hand, and the Connecticut Valley on 
the other, is a plateau or upland fringe bearing the same relation to the 
bordering ^mountains as the Piedmont Plateau of the southern Appa- 
lachians bears to the mountainous western border in Georgia and North 
and South Carolina. It is an upland composed in part of somewhat 
metamorphosed granite and diorite, in larger part of slates, schists, 
etc., derived by metamorphism from sedimentary rocks. Although 
much narrower than its southern representative it maintains continu- 
ously its identity as a border feature and possesses a well-marked 
physiographic character. It forms a transition upland between the 
eastern flanks of the Green Mountains and the lowland of the Con- 
necticut Valley in Connecticut, Massachusetts, and Vermont, and 
throughout its whole extent is much dissected by transverse south- 
eastward-trending valleys such as the Farmington in Connecticut, the 
Westfield in Massachusetts, and the White and the Williams rivers in 
Vermont. The uplands rise from a low southern margin on the shore of 
Long Island Sound to an elevation of 1000 feet at the northern bound- 
ary of Connecticut and to 1400 or 1600 feet at the northern boundary 
of Massachusetts. For the first score of miles the average rate is 20 feet 
per mile and is maintained with tolerable regularity. The ascent of the 
upland in Massachusetts is somewhat more gentle, from 10 to 12 feet 
per mile. 

Lying well within the border of the glaciated country of North America 
and constituting one of the two principal lines of elevations in New 
England it is natural that the Green Mountains should bear the marks 
of heavy glaciation. Strias and rounded knobs and bosses of rock, 
erratic bowlders and sheets and patches of till are the common features, 
while many of the lakes of Vermont within and without the Green 
Mountains are due either to glacial overdeepening of preglacial valleys 
or irregular deposition of drift or to both. 

The mountain summits are often bare rock ledges; the mountain 
flanks, especially on the west, are steep slopes with abundant rock out- 
crops and naked precipitous cliffs. Rarely are the mountain flanks 
soil-covered up to their summits, although a few such cases occur. 
Mount Stratton, one of the two highest peaks in southern Vermont, is 
completely covered with glacial debris even to its summit.^ 

The eastern slopes of the Green Mountains are the gentler and it is 
natural that we should find them more heavily cloaked with glacial 

> C. H. Hitchcock, Glaciation of the Green Mountain Range, Rept. State Geologist of 
Vermont, 1904, p. 75. 



6S2 



FOREST PHYSIOGRAPHY 



material. Especially do they have a covering on the lower slopes, which 
are cleared and farmed and form a pleasing contrast to the western 
slopes of the White Mountains on the opposite side of the Connecticut 
Valley. The narrow fringe of upland between the Green -Mountains 
and the Connecticut Valley, the northern representative of the Pied- 
mont Plateau, is also blanketed with glacial waste and both hills and 
valleys are dotted with homesteads. 

The abundant rainfall of the Green Mountains, a condition which 
they share with the rest of New England, offsets to some degree the dis- 




Fig. 262. — Forest growth on a steep and rocky New England hillside, Jamaica Plain, Mass. 



advantages of a thin soil, and though the forest growth is never luxuriant, 
it is, or was, in the main continuous. The lower valley slopes offer the 
deepest soil and the most sheltered positions and hence are most heavily 
timbered. The soil of the higher exposed situations supports a rela- 
tively thin forest of spruce and birch. The most favorable situations 



OLDER APPALACHIANS (NORTHERN DIVISION) 653 

for tree growth are the coves developed upon the older granites of the 
range, where the decayed rock is heavily cloaked with glacial till. 

Both the White and the Green mountains, as well asmany other portions 
of New England, have great tracts of ultimate forest land, that is to say, 
land which will bear trees more profitably than anything else and hence 
will be kept timbered when man's purposes become well adjusted to the 
soil. Indeed much of their surface will yield nothing but timber. It 
is surprising how healthy a growth will sometimes be developed upon 
a steep and almost barren hillside. Fig. 262. The clearing of such a 
situation rarely does great damage to the soil because the soil is so thin 
and stony (see p. 6), though if kept cleared it is subject to harmful 
erosion. Vigorous soil erosion is not, however, common on the unforested 
mountain slopes of New England. On the other hand, the effects of the 
forests on streams flow is clearly apparent. The slopes of the surface 
are sufificiently steep to enforce a dangerously heavy and rapid run-off 
were the timber cover and lake systems less extensive. 

Connecticut Valley Lowland 

general features 

The Connecticut Valley, or valley lowland, as it is sometimes called, 
is about 95 miles long. Its width varies from 5 miles at each end to 
15 or 18 miles in the middle. Its area is about 1000 square miles; a 
third of this is in Massachusetts, the rest in Connecticut. A slight 
uplift since Cretaceous peneplanation and the general occurrence of 
soft sandstones and shales have led to the development of a lowland 
(Tertiary) between an eastern and a western upland of crystalline rock 
of sufficient resistance to preserve traces of the peneplain. The greater 
part of the lowland is drained by the Connecticut River, although large 
portions are drained also by the Quinnipiac and the Farmington. 

GEOLOGIC STRUCTURE 

The lowermost rocks which constitute the Triassic formation of the 
Connecticut Valley consist of a series of 5000 to 6500 feet of coarse 
sandstone and conglomerate and a limited amount of shale. The 
material consists of the waste of granite and other crystalline rocks 
similar to those upon which the deposits lie. Intruded in these and 
generally not more than 200 to 300 feet above the base of the formation 
are the trap sheets of West Rock Ridge in the south and of the Barn- 
door Hills in the north. The sheets are from 500 to 600 feet thick in 



654 



FOREST PHYSIOGRAPHY 



XKw H.\Mi'siin;r 




Fig. 263. — Relation of the Connecticut Valley lowland to the bordering uplands, the extent of the low- 
land, principal relief features, and drainage systems. (Russell, Davis, and others, U. S. Geol. Surv.) 



OLDER APPALACHIANS (NORTHERN DIVISION) 



655 



places, but generally somewhat less. Succeeding the lower members 
with their intruded trap sheet is a series of sandstones, shales, impure 
limestones, intercalated with a series of three trap sheets. The lower 
trap sheet is called the anterior sheet and is generally about 250 feet 
thick, but thins out and disappears before reaching the northern bound- 
ary of Connecticut. Above the anterior sheet are shales and sandstones 




A-A'=Le-VBl reached by 
later cycles of erosion 



BY JOSEPH BARRELL 



SCALE IN MILES, HORIZONTAL AND VERTICAL 
SECTION IN CENTRAL CONNECTICUT 

THE NEW ENGLAND ALPS 

AT THE CLOSE OF 

THE APPALACHIAN KEVOLUTION 

Fig. 264. — The geologic and physiographic history of the Connecticut Valley lowland and adjacent 
portions of the bordering uplands. Vertical and horizontal distances to same scale. 

A. A time of great regional metamorphism and inferred volcanic activity. 




A-A'=.Level reached by 
later.cycles of erosion 



BY JOSEPH BARRELL 



SCALE IN MILES, HORIZONTAL AND VERTICAL 
BLOCK MOUNTAINS 

CENTRAL CONNECTICUT 

EARLY JURASSIC PERIOD 

B. After sedimentation had filled a structural depression and the strata had been block-faulted. 
temporaneous lavas are shown as black bands conformable with the strata. 



Con- 



656 



FOREST PHYSIOGRAPHY 




5 I 2 3 i 5 6 7 8 9 10 
SCALE IN MILES, HORIZONTAL AND VERTICAL 

CROSS SECTION 

CENTBAL CONNECTICUT 

IN THE CRETACEOUS PERIOD 
C. Appearance of the surface at the end of the Jurassic-Cretaceous cycle of erosion. 



BY JOSEPH BARRELL 



Wes-tern Upland 



£SMs. 



^.2^..^^ Mmj^^ l^Bh. 



.cSb 



Eastern Uprtand 




I TYLassic se.dime.nts 
Paleozoic intrusive granite-gneisses 
Paleozoic sediments 
Pre-Camb.rian complex gneisses 



3 4 5 6 7 8 9 10 BY JOSEPH BARRELL. 

S^ALE IN MILES^ HORIZONTAL AND VERTICAL 

CROSS SECTION 

CONJS^ECTICUT VALLEY 

IN CENTRAL' C0NNECTICT7T 

PRESENT GEOLOGIC TIME 



D. Following uplift there was more vigorous dissection of the softer sandstones, leaving the trap ridges 
and crystalline uplands in relief. 

from 300 to 1000 feet thick. Then comes the thickest and main trap 
sheet, 400 to 500 feet thick, another series of shales 1200 feet thick, and 
an uppermost or posterior trap sheet 100 to 150 feet thick. 

Originally the sediments were deposited in a nearly horizontal posi- 
tion, and had this position been maintained up to the present, the topog- 
raphy and drainage of the region would be far more simple than is the 
case to-day. It was while the sandstones were being deposited that the 
lava flows of the eastern trap sheets took place, and after they had been 
deposited that the igneous intrusions of the western trap sheets took 
place. There followed a period of deformation in which both sand- 
stones and trap sheets were extensively faulted and tilted, thus exposing 
the basset edges of both. 



FAULTS AND ASSOCIATED OVERLAPS 



The western range of trap ridges including West Rock Ridge and the 
Barndoor Hills of northern Connecticut have their successive members 
arranged en echelon. The southern ridges are arranged in advancing 



OLDER APPALACHIANS (NORTHERN DIVISION) 



657 



order, each northern ridge standing to the west of the next southern 
ridge, the ends overlapping by a moderate amount. In the northern 
group the arrangement is reversed; the order is receding and each 
northern ridge in succession stands farther east than the next southern 
ridge; and instead of the overlapping feature of the southern ridges 
there are gaps between the different members of the northern ridges, 
Fig. 265. 

The eastern trap ridges are greatly diversified as to form, size, and 
arrangement on account of differences in the thickness of the trap 
sheets and their greater number. Two features predominate. In the 
southern section two ridges are curved into the form of an irregular 
crescent convex to the northwest, the horns of the crescent extending 
almost to the eastern crystalline area. The other ridges, about 20 in 
number, are arranged in the same advancing and receding order that is 
exhibited in the western range, the advancing order being displayed ex- 
ceptionally well near Meriden, the retreating order about Tariffville, and 
the change from one to the other may be noted west of Hartford. 
Along the eastern ridges the main or middle 
trap ridge is of greater topographic promi- 
nence because of its greater thickness, 400 
to 500 feet. 

The advancing and retreating order of the 
trap ridges is explained by displacement along 
the faults that cross the Triassic formation 
diagonally from northeast to southwest. The 
ridge overlaps on the south and the gaps on 
the north are both the expression of a move- 
ment on the fault planes. In the one case 
(overlapping ridges) displacement resulted 
in offset with overlap, in the other case (gaps 
between ridges) displacement resulted in offset 
with gap. The movements in the two cases 
were in parallel lines but in opposite direc- 
tions. The application of this simple principle 
explains all the more prominent outlines of 
the topography of the district. The trans- 
verse diagonal faults just described are not 
confined to the Connecticut Valley. Just as 

they cross sandstones and traps, lowland and ridges, so they pass from 
the valley to the upland, into which they may in a few cases be traced. 
Upon the border of the upland they produce important indentations, 




Fig. 265. — Displacement of trap 
ridges near northern end of West 
Rock Ridge and corresponding 
displacement in the crystallines of 
the bordering uplands. (Davis.) 



6s8 



FOREST PHYSIOGRAPHY 



the chief ones being from South Glastonbury to South Manchester 
and from Vernon to Rockville, where the border of the eastern crystal- 
Hnes strikingly corresponds in northeast trend with the direction of 
the lines of major faulting in the Triassic. On the western border the 
faults of the lowland pass into the crystalline upland in a much less 
distinct manner, causing slight offsets and overlaps in the western bound- 
ary, Fig. 265. 

CRETACEOUS PENEPLAIN 

Except on the trap ridges the Cretaceous peneplain is now com- 
pletely destroyed in the Connecticut Valley. Upon the peneplain at 
the time of its full development the streams must have flowed in 
courses that were within certain wade limits independent of rock struc- 
ture and therefore of belts of hard and soft rock. The whole region 
was blanketed with a cover of residual soil upon which the streams 
were free to meander, perhaps only slightly controlled by the harder trap 
which may have persisted in the form of low flat-topped divides even 
during the time of most complete denudation. 



SUPERPOSED COURSE OF THE LOWER CONNECTICUT 

The Connecticut River, after flowing in a rather direct manner from 
north to south through the Connecticut Valley lowland, turns almost 
at right angles at Middletown and cuts through the crystalline rocks 

of the eastern upland as far as 
I, , d !.:.__;. the point of discharge near Say- 
brook. Such a course could not 
have been gained during the 
period of adjustment of streams 
to structures before the forma- 
tion of a peneplaned surface. 

The most reasonable explana- 
tion applied to the lower Con- 
necticut is as follows. The 
Cretaceous clays and sands out- 
cropping upon the northern shore 
of Long Island formerly extended 
farther north, overlapping the 
southern border of the Creta- 
ceous peneplain, Fig. 266. It is 
probable that they formerly overlapped the southern border of New 
England as far as Hartford. 




Fig. 266. — Inferred Cretaceous overlap on the 
southern shore of Connecticut. (Davis.) 



OLDER APPALACHIANS (NORTHERN DIVISION) 659 

The retreat of the shore Hne after the deposition of the Cretaceous 
overlap would allow an extension of all the streams down the slope of 
the coastal plain thus formed. The general slope of the plain would 
determine the general direction of the extended streams and the more 
detailed courses would be determined by the local irregularities of the 
surface. The stripping off of the overlapping Cretaceous cover would 
result in the gradual superposition of the lower courses of all the streams 
upon the underlying floor. It is clear that the lower courses might be 
directed across points of hard rock, across ridges, and from crystallines 
to sandstones and vice versa, in a manner only visible when the cover 
causing these complexities was extensively removed. After uplift and 
while the lower Connecticut was developing a narrow valley in the 
resistant crystallines, its tributaries developed a broad valley in the 
soft sandstones. 

It need not be supposed that the Cretaceous overlap was of great thickness to cause a com- 
plete turning aside of the streams from a course coincident with that which they formerly had 
upon the peneplain beneath the Cretaceous cover. The base-leveling was so nearly com- 
pleted that a cover of a hundred feet thickness, perhaps fifty feet, would conceal all but a very 
few of the low rounded hills that appeared as residuals above the general level of the pene- 
plain. It is even conceivable that the master stream of the region, the Connecticut, might 
have accumulated an exceptional amount of material upon the sea floor at its mouth and 
that when uplift occurred it would flow down the steepest slope of a broad fan, a course which 
might be on any radius. Conceiving the radius most favored as that directed most nearly to 
the east, the river would be turned from its former direction to one that would cause it later to 
be incised in the crystallines. 



TERTIARY PENEPLAIN 

The uplift of the Cretaceous peneplain and of the overlapping border 
of Cretaceous sediments enabled erosive agencies completely to remove 
the overlap and everywhere to dissect the uplifted peneplain. The uplift 
was accomplished not in one period of deformation but in two periods; 
for between the old Cretaceous level of the trap ridges and the present 
level of erosion one finds an intermediate level, a local Tertiary peneplain 
developed upon Triassic sandstones. It stands out conspicuously in 
certain views, being well developed north and northeast of Hartford, 
south of Mount Carmel, west of Mount Tom, and in many other locali- 
ties. During the time in which the Tertiary lowland was being formed 
the resistant trap rocks of the valley lowland and the only slightly less 
resistant crystallines of the uplands maintained approximately their old 
positions. 



66o FOREST PHYSIOGR.\PHY 



FORMS DUE TO SECOND UPLIFT AND TO GLACIATION 

The short Tertiary cycle was terminated by a second uplift which 
brought the land approximately to its present level and enabled the 
dissection of the uplands to be invigorated and that of the Tertiary 
plain to be begun. The last geologic event of importance in the region 
was glaciation, which, however, did not markedly affect the principal 
topographic and drainage outlines. The slopes of the hills and valleys 
were more or less thinly cloaked with rock waste, the debris of the con- 
tinental ice sheet. The tops of the ridges were in many cases notably 
rounded, smoothed, and striated, although they were presumably but 
little reduced in height. The lowland plain and the river valleys were 
everywhere made more irregular, and in many cases reversed slopes were 
produced back of which lake waters now lie. 

The most conspicuous drainage change was in the case of the Farmington River, which for- 
merly ran south from Round Hill and Farmington through the present valley of the Pequa- 
buck, through Plainville and Southington, and thence through the present Quinnipiac Valley 
to the Sound. But a low dam of glacial material at Plainville diverted the water of the river 
northward, with the result that from Farmington the river runs almost due north for about 
12 to IS miles to Tariffville, where it makes a sharp turn to the east and southeast, crosses 
the three trap sheets of the valley and pursues a more or less irregular course toward the south- 
east to the Connecticut at Windsor.i 

SOILS AND VEGETATION 

The soils of the Connecticut Valley are of many kinds, depending in 
part upon the many differences in rock character from place to place and 
in part upon different modes of origin. To understand the first cause of 
difference it is necessary to recall that though we commonly speak of 
a glacial soil as composed of foreign material, this is true only within 
certain rather narrow limits. Analyses made by Leverett and by Alden 
show that about 85 % of the till of the Great Lake region is derived 
from the underlying sedimentary rock. An even higher proportion of 
locally derived material is found in the Connecticut Valley. 

Such glacial forms as drumlins, eskers, sand plains, moraines, etc., 
have distinctive soil characters that are easy of identification. On 
account of their flatness and areal extent the sand plains of the Con- 
necticut Valley deserve special consideration. The material of the sand 
plains is commonly loose and porous, varies in texture from fine to 
coarse but is always prevailingly sandy, may have moderate natural 
fertility but is generally decidedly infertile as compared with the more 

1 Rice and Gregory, Manual of Connecticut Geol. Bull. Conn. Geol. and Nat. Hist. Surv. 
No. 6, 1906, pp. 251-253. 



OLDER APPALACHIANS (NORTHERN DIVISION) 



66l 



clayey soils of the till plains, and has a high absorptive capacity because 
of its flatness and porosity. Its loose nature, however, prevents it from 
retaining the absorbed water in large enough quantities and for long 




Fig. 267. — The North Haven sand plain, or "desert," five miles south of Wallingford, Conn. See the 
New Haven quadrangle, U. S. Geol. Surv. Part of Mt. Carmel in the background. Note the tufted 
grass {Andropogon scoparius) and the extent of bare surface. (Photograph by Beede.) 



enough periods as a rule to allow a maximum or even a favorable plant 
growth, and sand plains are commonly local semi-arid tracts in the midst 
of more fertile areas. 

One of the best illustrations of these features found in New England 
is the North Haven sand plain which stretches from Montowese (New 
Haven topographic sheet) to Wallingford, Connecticut, and beyond. It 
is about 15 miles long, with an average width of i to 2 or more miles. 
Its surface is in general flat or gently sloping; its soils vary in texture 
from a fine to a coarse sandy loam, with large areas of pure sand without 
a loamy admixture. The yellow sand shows distinctly through the 
thin cover of vegetation and gives such tracts a strikingly desert-like 
appearance. The water table stands from about 10 feet to 20 feet 
below the surface in spite of proximity to the river (Quinnipiac) and the 
fact that it receives the drainage from the adjacent upland portions 
of the drainage basin in which it occurs. Even after a heavy rain one 
can find little water in the soil except in the most favored portions. 
In places the scanty vegetation has a prosperous appearance, but in 



662 FOREST PHYSIOGRAPHY 

general distinctly xerophilous characteristics are displayed. Certain 
tracts support only grasses (chiefly Andropogon) which grow in scattered 
bunches. An elaborate botanical study of the vegetation of this area 
has been made with some interesting results.^ It has been found that 
while the lack of water is pronounced it is not this lack but the burning 
heat of the sun on the bare sand that enables only xerophytes to exist. 
Other plants perish soon after their seeds germinate. Among the peren- 
nial grasses, Andropogon furcatus has thickened root nodes in which 
food and moisture are stored up and carried through the winter. Andro- 
pogon scoparius is present in tufts, is the most abundant, and has a 
leaf whose upper surface is composed of an epidermis made up of water 
cells that constitute about one-third the total thickness. Similar or 
comparable adaptations have been found on nearly a dozen other annuals 
found within the area. 

On certain areas there is a regular order of occupation of the bare sand. The reindeer 
moss {Cladonia rangiferina) covers the bare sand, and where this lichen becomes established 
other plants spring up because the moss prevents the sand from shifting and entangles the 
seeds blown across it. Upon this undisturbed surface there accumulates in time a layer of 
leaf and vegetable mold that retards evaporation and enriches the soil, enabUng, through these 
more fortunate conditions, the germination and development of other more delicate plants. 
Sweet fern {Comptonia peregrina) may possibly follow the reindeer moss as the next stage 
in the development of a vegetal cover. The black cherry, with a tendency to form colonies 
by root sprouting; the common milkweed, also grows in colonies; and scrubby black oaks 
widely scattered throughout the area are common forms of larger growth. The prosperous 
condition of the larger trees and especially the oaks is noteworthy and appears to be due ia 
the case of the oaks to the length of the characteristic taproot. 

Each tree forms a sort of anchorage ground about which and under which acorns, grasses, 
mosses, and lichens grow or accumulate in some numbers. In time a mold is formed 
even at some distance from the parent tree, and in it acorns may sprout and thus gradually 
extend the vegetal covering. Once started the long taproot quickly reaches the ground 
water, and once in touch with this source of supply the life of the tree is assured barring acci- 
dent. The normal development of vegetation thus outlined is interfered with by fires, which 
burn the leaves and grasses and even burn out the mold from the surface soil, the element most 
needed for the reclamation of the area. One sample of the sand-plain soil at Montowese was 
found to contain but .09 of 1% of nitrogen, and it is probably to the nitrogen deficiency to 
which this points as much as to the dryness of the area that the absence of plant growth is 
due at any one time, though the more fundamental cause in the long run must be the relative 
dryness of the area and the shifting character of the surface. 

The soils of the Connecticut Valley (between Springfield and Hart- 
ford) are of many varieties and are most irregularly disposed. The so- 
called Suffield clay (glacial and interglacial), the Triassic stony loam, 
and the Holyoke stony loam (strictly glacial) are distributed in the 
most hit-and-miss manner imaginable. The fine sandy loams are com- 

1 W. E. Britton, Vegetation of the North Haven Sand Plain, Bull. Torrey Bot. Club, 
vol. 30, 1903, pp. 571-620 



OLDER APPALACHIANS (NORTHERN DIVISION) 663 

monly found along the stream courses and in terraces and valley flats, 
while the larger areas of undrained or poorly drained meadow land are 
found along the valley floors. Among the strictly glacial soils the 
Triassic stony loam is the most important. It is generally a fine sandy 
loam mixed with gravel and bowlders, the whole derived chiefly from 
the underlying Triassic sandstones. The amount of gravel and unde- 
composed rock in it exceeds 5% in all cases and in some cases exceeds 
50%. The stoniest loams of the Connecticut Valley sometimes contain 
from 10% to 50% of bowlders ranging in size from i inch to 15 inches 
in diameter. They are relatively infertile and are but little farmed, 
being given up mainly to stony pastures, wood lots, and orchards, with 
occasional patches of corn, oats, and rye. 

The exposed floor of the old glacial lake and river terraces in the 
Connecticut Valley are composed of yellowish-red or brown sand that 
contains less than 5% of clay. About 5% of the soil consists of coarse 
gravel and is inclined to be leachy and dry, though it is valuable for 
truck farming. The surface of the area is level or gently rolling in 
Connecticut; in Massachusetts it is much more rolling. The type is 
not very extensively cultivated, and in Connecticut there are but few 
houses upon it, the roads are deep and sandy, and along them are many 
old and unsuccessful fruit farms. Many areas of Windsor sand which 
were formerly cultivated are now grown up to a characteristic forest 
growth of pine. The soil is open and porous, offers little resistance to 
rains, and is so flat and so little washed that there are old well-preserved 
corn rows running through a forest in which the trees must be at least 
50 to 80 years old.^ 

On either side of the Connecticut River from Holyoke south to Long- 
meadow, Massachusetts, and from Warehouse Point to South Glaston- 
bury, Connecticut, are the Connecticut meadows or the present flood 
plain of the Connecticut River and its tributaries. The lower portions 
are frequently wet and swampy and subject to overflow, but in spite of 
this condition there is considerable farming on them at some risk. The 
character of the material is very uniform; it is a fine sand and silt 
16 to 18 inches deep, containing a large amount of organic matter. 
Below Merrick the meadows are diked to keep out the high water and 
to insure against overflow. The Connecticut meadows are among the 
most extensive and most important soils in the valley, with marked 
differences in texture, water-holding capacity, and warmth, and an 
equally marked difference in the quality of the products. 

» Dorsey and Bonsteel, Soil Survey in the Connecticut Valley, Rept. U. S. Bur. Soils No. 64, 
1900, p. 133. 



664 FOREST PHYSIOGRAPHY 

Scattered over the entire Connecticut Valley are considerable areas of 
swamp land and wet meadovv^. They generally occur along the scarps 
between the valley flats and upland where the ground water appears. 
The degree of swampiness precludes cultivation except where special 
drainage conditions are maintained. 



CHAPTER XXXI 
NEWER APPALACHIANS 

Introductory 

The Newer Appalachians are the most striking member of the Appa- 
lachian group of physiographic provinces. The subdivision includes 
rather regularly folded strata and long narrow valleys separated by 
nearly parallel ridges. It is marked by the presence of a great valley 




Fig. 268. — Relief map of the central part of the Appalachian System. (U. S. GeoJ. Surv.) 

which extends with but local and minor interruptions from end to end 
of the long province. This is not a single river valley but a composite 
of many valleys to which the name Great Appalachian Valley has been 
applied. The Coosa, Tennessee, Shenandoah, Cumberland, Middle 
Hudson, and Champlain valleys are its chief members. The Newer 
Appalachians province is bordered on the east by the Unaka Moun- 

66s 



666 FOREST PHYSIOGRAPHY 

tains, the Great Smoky Mountains and the Blue Ridge at the south, 
and by the Highlands of New Jersey and the Green Mountains at the 
north; on the west it is bordered by the Cumberland Escarpment, the 
Allegheny Front, the Catskills, and the Adirondacks. 

The southern portion of the Great Appalachian Valley is limited on 
the west by the eastern edge of the Appalachian Plateaus, whose vari- 
ous sections are here designated Walden Ridge, Lookout Mountain, and 
Sands Mountain. These plateau remnants have a heavy sandstone cap 
and their margins are defended by heavy and extremely resistant beds 
of sandstone and conglomerate. They are commonly from 800 to 1000 
feet high and on the east overlook the Great Appalachian Valley as a 
bold scarp — the Cumberland Escarpment — which forms as definite a 
border to the Great Valley on the west as the southern Appalachians 
do on 'the east. 

In a broad view the Newer Appalachians consist more largely of 
valleys and valley lowlands than of ridges in the Chattanooga region 
on the south and the Champlain-Hudson region on the north. In the 
central portion of the province the mountain and not the valley feature 
is on the whole the more prominent. Fig. 268; only the eastern side of 
the central district is marked by broad valleys, as the Shenandoah 
Valley of Virginia, developed on less resistant limestones, the Cumber- 
land Valley of Maryland and Pennsylvania, and the Lebanon Valley of 
eastern Pennsylvania. On the basis of these topographic differences it 
will be convenient to subdivide the Newer Appalachians into three dis- 
tricts, a southern, a central, and a northern district. 

The rock formations change from point to point somewhat, but their 
most striking characteristics are their continuity and lack of variation 
through long distances. In general they are more limey at the south 
and sandy and conglomeratic at the north. There are also important 
differences of structure such as the presence of great overthrust faults 
in the Chattanooga district and the general absence of these structural 
features and related topographic forms in the Pennsylvania ridges. In 
the former district the presence of great thicknesses of easily eroded 
strata such as limestone and shale, structurally deformed so as to expose 
on erosion the edges of the strata, has resulted in profound denudation 
and the carrying away of at least 10,000 feet of rock. 

Southern District 

A prominent feature of the southern district of the Newer Appa- 
lachians is the number of ridges that follow exactly in line with the topo- 
graphic level maintained by Walden Ridge and Cumberland Plateau, 



NEWER APPALACHIANS 667 

Fig. 238. These ridge summits constitute, however, but a small portion 
of the entire area, for since the uplift of the Cretaceous (Cumberland) 
peneplain the greater part of it has been removed by erosion. This 
is due both to the relatively soft rock of the district and to the com- 
pressed nature of the folds, which reveal the beds in nearly vertical 
attitudes and so permit greater erosion. Such ridges as occur are, 
however, very even-crested in spite of considerable diversity in rock 
character, and are unquestionably the remnants of a former more 
extensive plain. 

In places the ridges depart somewhat from the general type and seem to rise above the 
level of the peneplain. In such cases the wind gaps probably represent the old base level, for 
• they have a constant altitude, whereas the intervening portions of the ridges rise irregularly 
from 100 to 300 feet above them, and were probably a series of knobs projecting above the 
peneplain level. In contrast to these exceptional features are the ridges composed of less 
resistant rock or occupying more exposed positions. These have been so reduced by erosion 
following upon the uphft of the Cretaceous peneplain that no point along their crests attains 
the altitude of the peneplain. On the whole, however, the ridges are surprisingly accordant 
in altitude and their level is nearly always harmonious with that of adjacent, better preserved 
portions of the plain. 

The early Tertiary (Highland Rim) peneplain was not developed so 
extensively as the Cretaceous peneplain within the borders of this dis- 
trict. Its chief development was along the larger valleys where narrow 
belts of rock were planed to a more or less level expression. Rem- 
nants of it may still be seen at altitudes above 1000 feet, where the 
great majority of hills and ridges may be seen to reach nearly to a com- 
mon level. Standing above this topographic level are a number of 
residuals among which White Oak Mountain, Tenn., is the most promi- 
nent. Like the Cretaceous cycle the early Tertiary cycle was closed by 
irregular uplift, the first result of which was to invigorate the streams 
and cause them to incise valleys below the general level. Gradually 
the valleys were widened to form local lowlands upon areas of softer 
rock. The result was a partial planation of a region distinctly smaller 
than that peneplaned during the early Tertiary cycle and only a fraction 
as large as the great area peneplaned during the Cretaceous cycle. 
This local lowland has been called the Coosa peneplain because of its 
excellent development along Coosa River (see Fig. 235). 

The Coosa "Flat Woods" are the largest unit of this peneplain. They form a belt 10 
to 12 miles wide and but little above the narrow flood plain of the river though never reached 
by the present floods. The peneplain is developed upon soft or soluble rocks, limestones, and 
limey shales; where the Coosa flows upon more resistant formations the valley is compara- 
tively narrow. The altitude of the Coosa peneplain is more than 700 feet at the southern 
margin of the Chattanooga district and about 800 feet at the northern margin. The slope is 
Httle more than the normal grade of a base-leveled surface, which shows that but slight local 
deformation has occurred, although when examined in detail considerable variation in alti- 
tude is expressed in the various portions of the peneplain. 



668 FOREST PHYSIOGRAPHY 

Stream Types 

The topographic changes outlined above took place during immensely 
long intervals of time, and if were call the physiographic principles of 
stream adjustment, the constant shifting of stream courses through the 
more rapid development of those which flow upon belts of softer rock, 
we shall be prepared to appreciate the fact that very extensive stream 
changes have occurred in the Appalachian region. These have been 
conditioned by (i) the exposure of softer beds by the erosion of harder 
beds overlying them and (2) crustal warping which terminated each 
cycle and deformed the successive peneplains. 

A number of types of streams may be identified; the characteristics 
of these we shall sketch here only in the briefest manner. The first 
type is that represented by the Hiwassee, the New-Kanawha, and 
other streams which flow westward from the southern Appalachian 
mountains. The most striking member of this group is the New- 
Kanawha, which drains portions of all three physiographic provinces in 
succession from the Appalachian Mountains to the Appalachian Pla- 
teaus, Fig. 235. It appears to be an antecedent stream in that it has 
maintained its course westward against all the deformations which have 
been produced in its path. Its age must be measured in millions of 
years, for it probably dates from the great Appalachian revolution of 
Permian time, and though it has suffered many slight vicissitudes and 
its course has been opposed by mountain-making movements, the river 
has been victorious in all its. contests and still pursues its ancient 
northwestward course. 

The present course of Tennessee River has topographic relations of 
equal interest. After flowing southwest for several hundred miles, as 
far as Chattanooga, it turns sharply west, crosses the high plateau 
known as Walden Ridge, then turns sharply southwestward again, and 
flows in another straight stretch for over 200 miles before turning 
north to join the Ohio. Its course across Walden Ridge corresponds 
to the course of the river upon the Cretaceous peneplain. It is very 
strikingly meandering, and under other circumstances the meanders 
would be accepted without question as inheritances from a low- 
gradient strongly meandering stream later incised in a formation so 
hard as to preserve them in somewhat their original form or a derived 
form not departing much from the original pattern. When taken with 
the other evidence these meanders may be regarded as safely referable 
to this mode of origin. That they have been preserved for such a long 
period as all of Cretaceous time does not seem unreasonable when it is 



NEWER APPALACHIANS 669 

recalled that only the lower 100 to 200 feet of the 1000-foot gorge across 
Walden Ridge is composed of soft limestone, while all the rest of this 
great section exposes extremely resistant sandstone.^ The great thick- 
ness of the resistant strata has prevented the river from widening its 
valley in precisely the manner in which the hard strata of the Kitta- 
tinny anticline in New Jersey have restrained valley development along 
the Delaware and made possible the formation of the Delaware water 
gap. During the time that the Delaware River was cutting the gorge 
at the water gap the tributaries and their auxiliary streams were widen- 
ing the soft formations on either side and developing them into the 
form of a broad valley lowland. The strong differences in rock char- 
acter between the Sequatchie anticline and the Appalachian Valley on 
the one hand, and the Walden and Cumberland plateaus on the other, 
are not less than the differences among the valley widths of the streams 
or portions of streams flowing through these formations. 

A second type of drainage is that which represents the effects of 
wandering during the later stages of an erosion cycle. This is considered 
to be an explanation of the course of the Ocoee where it crosses or is 
superimposed upon the point of Bean Mountain. 

A third class of stream is that found in the longitudinal valleys of the 
Newer Appalachians. It requires little explanation, for it is obvious 
that it belongs to the type known as subsequent rivers. When the 
Cretaceous peneplain was uplifted erosion went forward rapidty along 
belts of weak rock, and tributary streams originating in such belts 
rapidly extended their valleys headward. Those streams which crossed 
harder strata were prevented from lowering their channels at the same 
rate and eventually numbers of them were beheaded and made tribu- 
taries of their more powerful rivals. The abandoned channels across 
the hard ridge makers stood at higher and higher levels as the softer 
rocks were lowered on both sides; they now appear as wind gaps. Many 
streams are made up of sections which belong to different types. Their 
headwaters descend the western slopes of the southern Appalachians as 
originally, their middle courses occupy subsequent valleys arranged longi- 
tudinally, and their lower courses are superposed upon structures across 
which the streams flowed while working at the level of the Cretaceous 
peneplain. 

I The data for this paragraph are chiefly from the admirable discussion of the Tennessee 
problem in a paper by D. W. Johnson, The Tertiary History of the Tennessee River, Jour. 
Geol., vol. 13, 190S, pp. 194-231. The paper also contains a bibliography of the literature 
bearing on the Tennessee problem. 



670 * FOREST PHYSIOGRAPHY 

Central District 

The eastern boundary of the central district of the Newer Appa- 
lachians is the Blue Ridge; the Allegheny Front forms the western bound- 
ary. The latter is rugged and bold and faces southeast. It is the 
eastern edge of the Appalachian Plateaus and extends from the northern 
end of the Cumberland Plateau through West Virginia, Maryland, and 
Pennsylvania, and is continued northeastward more irregularly as far 
as the Catskill Mountains. 

Prominent points upon it are Dans Mountain, Maryland, 2100 feet above the sea; the Pin- 
nacle, West Virginia, 3400 feet; Roaring Plains, 4400 feet; the Big Black Mountains of Vir- 
ginia and Kentucky, 4000 feet; southward the summit becomes lower and at Cumberland Gap 
is but 1600 feet high. 

It is crossed by many streams such as the New, the Potomac, etc., 
but not enough dissection has taken place to destroy its wall-like char- 
acter throughout most of its extent. Narrow thousand-foot canyons 
are cut in it here and there, and between them are straight stretches of 
precipice often crowned by a resistant sandstone that stands out under 
weathering and erosion as a steep brow.'^ 

From the Maryland line northward a distance of about 50 miles the 
crest of the Front is rather broad and flat and nearly straight, at a 
fairly uniform elevation of between 2500 and 2700 feet. Above this level 
occasional knobs rise to heights of 3000 or more feet, as Blue Knob, 
15 miles south of Gallitzin, 3136 feet, the highest point in the state. 

From above or from a distance the lower part of the Allegheny Front 
in Pennsylvania appears as a grand terrace, made by the even tops of 
a series of projecting spurs that break the descent of the scarp. They 
are due to the presence of a second resistant formation, and as the crest 
of the Front becomes lower toward the northeast the terrace is entirely 
absent. This feature is nowhere better shown than near Altoona. The 
lower plain in that locality stands at 1200 feet, from which there is a 
moderately steep ascent to 1600 or 1700 feet, over a terrace belt from 
I mile to 1 1 miles wide. From the terrace there is an abrupt rise to 
the crest of the escarpment 2400 to 2700 feet high. 

The Allegheny Front crosses Pennsylvania in a sweeping curve 
toward the northeast for a distance of 230 miles, until it merges ob- 
scurely with the zigzags of the anthracite region in the northeastern 
corner of the state. The escarpment is broken only by narrow ravines 
through which flow the northern branches of the Susquehanna, the 
North Branch, Muncy, Loyalsock, Lycoming and Pine creeks, the West 

» Bailey Willis, The Northern Appalachians, Nat. Geog. Mon., i8g6, pp. 172-173. 



NEWER APPALACHIANS 67 1 

Branch, and Beech Creek. South of the gorge of Beech Creek the 
Front is unbroken by any large stream, though many steep ravines 
notch its crest and offer practicable routes of communication with the 
regions beyond. 

The larger main streams have cut narrow and steep-sided valleys 
500 or more feet deep, as well shown by the transverse course of the 
Youghiogheny. The smaller tributaries, especially in their upper por- 
tions west and north of the escarpment, have wider valley floors, and 
flow in relatively shallow valleys, often not more than 100 feet deep.^ 

The western part of the central district of the Newer Appalachians 
consists of closely folded strata that outcrop in the form of ridges with 
alternating narrow valleys, and the mountain, not the valley, feature is 
most prominent. Furthermore, the ridge crests almost everywhere reach 
to the level of the plateau on the west and exceed the elevation of the 
Blue Ridge on the east. 

The most persistent characteristic of the Appalachian ridges of the 
central district is the even character of the sky line as determined by 
the level-topped ridges and the accordant altitudes of the hilltops. 
Only here and there are the ridges interrupted by gaps where super- 
posed streams have maintained their courses across the ridges as they 
were gradually brought out to a strong topographic expression by 
differential erosion. A commanding point such as the summit of a 
residual surmounting the general level of the country affords a fine 
view out over a broad landscape. If the valleys and lowlands, now 
sunk below the general level, were filled up, the country would appear 
as a vast gently rolling plain of slight relief — an approximation to the 
condition that existed at the end of the Jurassic-Cretaceous cycle of 
erosion when the mountains formed during the great Appalachian 
Revolution were reduced to the condition of an almost featureless plain. 
This fact forms the starting point in all the physiographic considerations 
that follow concerning the Appalachian region as a whole, for it is in 
the erosion cycles that have followed and out of the peneplain that 
existed at the beginning of the Tertiary periods of degradation that all 
the later forms have been carved and the drainage features developed. 

The distinctive features of Appalachian topography in Pennsylvania, 
Maryland, and Virginia are long, parallel, sharp-crested ridges, often 
with zigzag pattern, Fig. 268, and with narrow valleys intervening. 
Adjoining ridges are often markedly parallel. They are in places de- 
veloped upon anticlines that expose resistant strata, in places upon 

1 W. S. Tower, Regional and Economic Geography of Pennsylvania (Physiography), Bull. 
Geog. Soc. Phil., vol. 4, 1906, pp. 205-206. 



672 FOREST PHYSIOGRAPHY 

synclines, and in others upon strata with a more complex internal struc- 
ture. All the larger valleys have their positions and directions deter- 
mined by the more yielding rocks and have been developed subsequent 
to both the deformation of the strata and the base-leveling that is respon- 
sible for the even-topped character of the ridges.^ 

Eleven principal mountain folds occur between the Blue Ridge on the southeast and the 
Allegheny Front on the northwest, in a distance of 49 miles. Claypole suggested that the 
amount of crustal shortening involved in the flexing of these folds meant a reduction to 65 
miles of a surface that originally measured 153 miles.2 Chamberlin's later and more accurate 
measurements show a compression into 66 miles of an original surface of 81 miles in a section 
west of Harrisburg.3 

Single folds more than 300 miles long are known in the Appalachian region, but the lengths 
of individual folds are more commonly from 25 to 50 miles. The intensity of the folding increases 
from east to west throughout the length of the province. In the Appalachian Plateaus the 
folds are very gentle, with dips generally less than 10°, and there is a close approach to horizon- 
tality on the west. The rocks are unaltered, even the shales being free from cleavage planes. 
In the Newer Appalachians the folding was more intense, the dips are generally 30° or more, 
and in many areas the rocks are nearly vertical. Most of the folds are symmetrical, with 
shorter, steeper northwest sides, and longer, gentler southeast sides, and many of them are 
overturned. The result is that the northwestern is the shorter and steeper and the south- 
eastern the longer and gentler of the mountain aspects. The structural folds are of consider- 
able magnitude, reaching 5 miles or more in vertical dimension between the larger folds, and 
are not simply a unit, being composed of numerous minor folds and these in turn of still smaller 
folds down to minute wrinkles.* 

A number of facts are essential to the understanding of the physiog- 
raphy of the zigzag ridges of the Newer Appalachians: (a) the Appa- 
lachian type of structure prevails throughout the region, that is to say, 
a series of rather regularly folded strata, the folds being in the form of 
more or less regular anticlines and synclines; (b) these folds have been 
base-leveled or peneplaned, so that by the end of the Cretaceous cycle of 
erosion the surface of the country had been worn down nearly to a plane 
surface; (c) the fact of base-leveling of these folds means, further, that 
hard and soft rocks were at one time exposed in belts but with only the 
faintest topographic expression; and (d) naturally all the rock strata 
would be exposed almost in the same plane, for the topographic cycle 
was long enough not only quickly to bring down the soft rocks to base 
level but also finally to reduce even the most stubborn members almost 
to the general level. 

(e) Uplift then occurred in the region and opportunity was afforded 
for the rejuvenation of the streams, the belts of soft rock were worn 

1 Topographic and Geological Survey of Pennsylvania, 1 906-1 908, p. in. 

2 E. W. Claypole, Pennsylvania before and after the Elevation of the Appalachian Moun- 
tains, Amer. Nat., vol. 19, 1885, pp. 257-265. 

5 R. T. ChamberHn, The Appalachian Folds of Central Pennsylvania, Jour. Geol., vol. 18 
1910, pp. 228-251. 

< G. W. Stose, Mercersburg-Chambersburg Folio U. S. Geol. Surv. No. 170, 1910, p. 13. 



NEWER APPALACHIANS 673 

quickly down approximately to the new base level, while the harder rock 
belts stood out as ridges whose summits now present to our belated 
sight the ancient level of the Cretaceous peneplain. The ridges are 
even-topped because they were all worn even by the end of the earliest 
erosion cycle, and time enough has not elapsed since the uplift of the 
region and the development of extensive lowlands by differential erosion 
for the ridges to be very much affected by erosion. The material com- 
posing them is most resistant conglomerate (Pottsville) and a stubborn 
sandstone (Medina and Pocono), and when compared with the soft 
Coal Measures and the slates (Hudson River) and shales (Mauch 
Chunk) these offer incomparably greater resistance. 

A sixth and last fact must be observed: (/) the axes of the folds are 
not horizontal for any distance, but pitch below the level of the peneplain, 
now at steep angles, now at gentle angles. Upon this feature depends 
the degree of divergence of the ridges. If the axes of the folds pitch at 
a steep angle the more strongly divergent will the ridges be formed; and 
conversely, the gentler the pitch the more narrow the angle between the 
ridges, the limit being parallelism, which would appear only when the 
folds became actually horizontal. According as the original folds were 
broad and gently pitching, or narrow and steeply pitching, the zigzags 
are long and wide or short and narrow. 

The best example of zigzag ridges is the double series at the western 
end of the anthracite coal region, where the ridge crests loop back and 
forth as Catawissa and Line, Manhantango and Berry, and Peter's and 
Second mountains. Following the same course, essentially parallel to 
the first, and contained within them, is the second set, Big and Mahanoy, 
Coal and Lock, and Stony and Sharp mountains. Another example 
is in the Buffalo or Seven Mountains (Center and Clinton counties, 
Pennsylvania), where a group of narrow folds, steeply pitching, has 
given a series of short zigzag ridges with 7 loops to the northeast and 
7 to the southwest."^ 

The student who will keep these groups of facts before him will be 
able to understand practically all the problems that the Appalachian 
ridges afford. A great variety of relief features can be assigned at 
once to their proper categories and order maintained in the examina- 
tion of a group of data that at first sight may seem very complex. They 
furnish the key to the solid geometry of the region, for it is solid geome- 
try, or a conception of three space dimensions, that is necessary in under- 
standing the zigzag ridges of Pennsylvania. 

1 W. S. Tower, Regional and Economic Geography of Pennsylvania (Physiography), Bull. 
Geog. Soc. Phil., vol. 4, 1906, p. 14. 



674 



FOREST PHYSIOGRAPHY 




''('/ //////^//'P//i'/ 



Fig. 269. — The half-cigar-shaped mountains developed on the hard rocks and the arches formed by the 
beds of an anticline. (Willis, U. S. Geol. Surv.) 




Fig. 270. — The canoe-shaped ridges of hard rocks and the arches formed by the beds of a syncline. 
(Willis, U. S. Geol. Surv.) 



NEWER APPALACHIANS 675 

Because of the gentle inner slopes and steep outer slopes the topo- 
graphic forms of the zigzag ridges have been likened to a canoe, and the 
resemblance is the more striking when it is recognized that the end of 
a synclinal mountain where it often meets in a rather sharp V is doubly 
resistant and usually stands out as a not quite reduced portion of the 
mountain region, a terminal knob suggesting the high prow of a canoe. 

In the case of the anticlinal mountains as in Fig. 269 the strata dip 
outward as represented, and the unroofing of the anticline by pene- 
planation and subsequent valley excavation in the belts of softer rock 
has produced a group of mountain forms in sharp contrast to the forms 
of synclinal mountains. The steep slopes are here on the inside of the 
fold and the gentle ones on the outside. Fundamentally the law is 
the same in both synclines and anticlines, for in both cases the gentle 
slopes are down the dip of the strata and the steep slopes are those 
formed across the strata. It is the difference of direction and dip in 
the two cases that has produced the slope contrasts. Were the strata 
arched across the gap in the heart of the fold the resulting form 
would roughly resemble a cigar tapering down at one or both ends, so 
this type of mountain is described as cigar-shaped. Variations of form 
and degree of contrast of opposite slopes depend, as in the case of the 
synclinal mountains, upon the degree of dip of the strata. And like the 
synclinal mountain the meeting of the two ridge makers at the terminal 
point of the mountain doubles the resistance at that point and produces 
a terminal knob which in many cases exists as a residual] or monadnock 
upon the surface of the peneplain. 

It is important to see how a region may exhibit either or both syncli- 
nal and anticlinal mountains. The actual condition at a given place 
will depend upon the relation of the plane of base-leveling to the hard 
and soft strata. In A, Fig. 272, the plane of base-leveling is in such 
relation to the hard layer i that during the cycle of erosion terminating 
in the complete reduction of the land surface, the hard layer i is 
completely removed and hard layer 3 exposed but not removed from 
the underlying soft layers. When uplift opens the next cycle of ero- 
sion all the mountains will be for a time anticlinal and all the valleys 
will be synclinal. In B, by the same process of reasoning, half the 
mountains would be synclinal and half anticlinal and the valleys would 
be correspondingly disposed. In C all the mountains would be synclinal. 
In a region never base-leveled but for the first time passing through a 
period of subaerial denudation the changes of form and their relations 
to structure are brought out in Fig. 271, provided the region is still 
above base level. 



676 FOREST PHYSIOGRAPHY 

Since a large number of the mountain systems of the earth have 
passed through one or more partial or complete cycles of topographic 
development, it is clear that a knowledge of the position of the plane 



Fig. 271. — The development of anticlinal valleys and synclinal mountains from an original consequent 
drainage has been established in a region with Appalachian structure. (Martonne, Traite de 
Geographie Physique, Armand Colin.) 

of base-leveling to the resistant rock strata, or ridge makers, is a matter 
of fundamental importance. In the Appalachian region the plane of 
base-leveling appears to have cut through the strata in such a manner 
as to form a larger number of anticlinal than synclinal mountains, 
though the latter type are numerous. The diagram Fig. 272-C roughly 



NEWER APPALACHIANS 



677 



represents the actual conditions in the central Appalachians. Horse 
Valley opposite Chambersburg, and Bear Meadows north of Hunting- 
don, Pennsylvania, are good examples of synclinal valleys.^ 

The most striking features of the valleys of the zigzag ridges, whether 
of one structure or another, are their linear extent and shut-in or cove- 
like character. Bald Eagle and Black Log Valleys, Penn., are typical. 
Kishicoquillis Valley, between Stone and Jack's Mountains in Miflflin 






C. 

Fig. 272. — Varying positions of the plane of base-leveling to hard and soft strata and their relation to anti- 
clinal and synclinal mountains, i and 2 represent hard layers; 3 represents a soft layer; x — x' 
represents the plane of base-leveling. In A the plane of base-leveling lies below i and intersects 2; 
in B it intersects both i and 2; in C it lies above 2 and intersects i. After uplift of the base-leveled 
surface the early stages of the erosion cycle will be marked by anticlinal mountains in A, anticlinal 
and synclinal mountains in B, and synclinal mountains in C. 

County, 53 miles long and 4 miles wide, is completely isolated except 
for the single outlet of Logan's Gap, near Lewiston. Tuscarora Valley 
is 50 miles long and 5 miles wide. Path and Nittany valleys are both 
over 30 miles long and from 2 to 5 miles wide, with no easy outlets 
except through an occasional water gap or over a higher wind gap. 
The sharp contrast between the linear extent and the width of the 
valleys is a direct result of the attitude of the strata, giving broader 
valleys where the strata are gently inclined and narrower valleys where 
steeply inclined.^ 

1 W. S. Tower, Regional and Economic Geography of Pennsylvania (Physiography), Bull. 
Geog. See. Phil., vol. 4, igo6, p. 128. 
' Idem, p. 128. 



678 FOREST PHYSIOGRAPHY 

Variations upon the simple scheme outlined above are not difficult to understand. If 
for example each anticline and each syncline has several hard ridge makers, instead of one, 
several parallel ridges will come into existence as in Figs. 269 and 270, which represent the actual 
conditions in the northern Appalachians in the region north of Harrisburg. The number of ridges 
that will occur in a given place will depend upon the size of the folds and the number of alter- 
nations of hard and soft strata. This rule may be stated in another way as follows: As many 
hard layers as are truncated by the plane of base-leveling will stand forth as ridges in the 
following cycle, and theoretically this number is limited only by the ability of the rock to be 
compressed into folds. Obviously a mass of strata may be so thick that it can not be compressed 
in such a manner as to form folds exposing the entire section in the form of regular anticlines 
and synchnes. The limit may be placed somewhere around 50,000 feet. A section across 
such a repeated series of ridge makers in a single fold appears as in Fig. 269. If the hard 
layers are sufficiently far apart, then each fold will repeat the idea], features shown in the figures 
above. If they are separated by a very thin soft layer the valleys between the ridge makers 
will not be deep unless the dip of the strata is unusually great. The two sides of a given ridge 
maker under these circumstances are also apt not to be so sharply contrasted as in the case 
where sufficient space occurs between the ridges for the formation of a large valley. 

No less striking than the topographic features of the zigzag ridges of 
the central district are the drainage features of the region. The master 
streams flow roughly at right angles to the trends of the ridges and 
cut across them through water gaps of notable depth and often of pro- 
nounced beauty. The course of the Delaware through the Delaware 
water gap, the Susquehanna through the gaps of the central Pennsyl- 
vania ridges above Harrisburg, and the prominent gaps of the Potomac 
through the same or similar ridges farther south are illustrations of 
this feature. Where they cross the ridges in the gorge-like water gaps 
the main streams are swift, often descending short rapids, while across 
the intervening valleys they often flow lazily and in regularly meander- 
ing courses.^ 

Perhaps the chief cause for the wholesale modification of the drainage 
of a given region such as will bring the streams into courses directly 
across the grain of the country, as in the case in hand, is the warping or 
bowing of the surface that commonly takes place after or during the 
late stages of peneplanation and inaugurates a new cycle of erosion 
or forms one of the late substages of the first cycle. The effect of 
such warping or bowing is to cause a migration of the divides toward 
the main axis of uplift as determined by Campbell^ and away from 
the area of subsidence. The antecedent drainage tends to become 
adjusted to the warped condition; streams come to occupy axes of 
depression, and divides finally become located on the axes of elevation. 
We have seen in Fig. 237 and accompanying text that the Appalachian 

1 W. S. Tower, Regional and Economic Geography of Pennsylvania (Physiography), Bull. 
Geog. Soc. Phil., vol. 4, 1906, p. 133. 

2 M. R. Campbell, Drainage Modifications and their laterpretation, Jour. Geol., vol. 4, 
1896, pp. 567-581, 657-678. 



NEWER APPALACHIANS 679 

region was bowed or warped up along a southwestward-trending axis 
located in western Pennsylvania and probably continuous with the axis 
in the southern Appalachians located by Hayes and Campbell in the 
vicinity of the Cumberland Plateau. While all the master streams do 
not have divides on this axis — the exceptions are the Tennessee, the 
New-Kanawha, and others — most of the streams conform to the 
general law applicable to the case. 

As intrenchment progresses after uplift and other erosive agencies 
are set into operation differential erosion will follow, hard rock will be 
exposed in patterns sympathetic with respect to structure, and there 
will be brought about a most unsympathetic relation between the 
topography and the drainage, precisely the sort of drainage that now 
exists between the main streams and the main lines of relief within 
the central district. The weaker tributary streams will for a time 
flow across the harder ridges like the master streams, but the steady 
development of subsequent streams along belts of weak rock that 
occupy the inter-ridge spaces will in time effect an almost complete 
adjustment of tributary streams to structure. This wholesale readjust- 
ment means stream capture on a most extensive scale. The gradual 
headward growth will be accompanied by progressive capture of streams 
at the disadvantage of crossing the harder ridges to reach the main 
streams. The old water gaps will become wind gaps and a diminished 
river will flow in the channel of the beheaded stream. Here and there 
a larger tributary or one with exceptional advantages will persist like 
its master stream. From the map. Fig. 235, one may see all degrees 
of adjustment as outlined above. ^ 

Northern District 

The northern district of the Newer Appalachians consists of a number 
of well-defined valleys and ridges whose structural features are more 
complex than those of the central district. The topography is not 
capable of an analysis as simple as in the case of either the Pennsyl- 
vania zigzags or the ridges and valleys of the Chattanooga district; 
the ridges and valleys are here less regular both in general and in detail. 
In respect of border features the northern district is unlike either of the 
other districts of the Newer Appalachians. On the west the province is 
terminated not by a single plateau but by an outlier of the great Lauren- 

' For an excellent description of the features of northern Pennsylvania and New Jersey 
with respect to drainage, see Davis and Wood, The Geographic Development of North- 
ern New Jersey, Boston Soc. Nat. Hist. Proc, vol. 24, i8go, pp. 365-423, and W. M. Davis, 
The Rivers and Valleys of Pennsylvania, Nat. Geog. Mag., vol. i, 1889, pp. 183-253. 



68o 



FOREST PHYSIOGRAPHY 




NEWER APPALACHIANS 68 1 

tian area of Canada, the Adirondacks, and by an exceptionally high and 
rugged portion of the Appalachian Plateaus, the Catskill Mountains. 
The northern district of the Newer Appalachians is also unlike the 
other districts in that the mountains upon its eastern border consist 
partly of metamorphosed rock, the schists of the Taconic and Moimt 
Greylock ranges. 

The Newer Appalachians have a very restricted development in 
northwestern New Jersey, but shortly after entering New York state 
and specifically in the Walkill and Middle Hudson valleys the Hudson 
River shales thicken greatly and the whole belt has a notably broader 
development. Between the Highlands of the Hudson and the Catskills 
a broad valley lowland has been formed which continues northward 
along the eastern border of the state to a point between Hudson and 
Renssela-er, where the southern outliers of the Taconic mountains begin. 
From this point northward the relatively soft Hudson River shales are 
restricted to a narrower belt and the mountain feature of the Newer 
Appalachians becomes more prominent. The principal topographic fea- 
ture of the district is the Taconic Range. Its geographic position and 
subdivisions are shown on the map, Figs. 273 and 274. The broadest 
development of the mountain group of which it forms a part is between 
the Hudson and the Hoosic valleys, roughly on the parallel of Troy. 
At this point the Newer Appalachians consist of the following members 
named in order from west to east: (i) the Hudson Valley, (2) the 
Rensselaer Plateau, (3) the Little Hoosic Valley, (4) the Taconic Range, 
including the Mount Greylock spur of the main Taconic Range, and (5) 
the upper portions of both the Hoosic and Housatonic valleys. From 
this point northward the Taconic mountains extend as a narrower 
range as far as northern Vermont, where they terminate. The total 
length of the range is about 200 miles, its width is from 5 to 10 miles. 
Its course is somewhat serpentine, with a north-northwest trend 
near Great Barrington, north-northeast to Dorset, and similar turns 
farther north.^ 

Many of the forms of the Taconic region are directly or indirectly 

1 The name "Berkshire Hills" is so commonly employed to designate portions of the region 
here discussed that a word as to its usage is in point. Dale (The Rensselaer Grit Plateau in 
New York, 13th Ann. Rept. U. S. Geol. Surv., pt. 2, 1801-92, p. 297) implies a restriction of 
the term to the Taconic Range and. the Greylock offshoot or the rugged country between the 
headwaters of the Hoosic and Housatonic rivers on the east and the western foot of the Ta- 
conic Range. Emerson's usage (Holyoke Folio U. S. Geol. Surv. No. 50, 1898, p. i) corre- 
sponds to that of the inhabitants of the region and includes all the hills and mountains of 
Berkshire County, Massachusetts. In this usage the Hoosac Mountains, the southern continu- 
ation of the Green Mountains of Vermont, or what is called in Massachusetts the western edge 
of the Green Mountains Plateau, are included with the Taconics in the term " Berkshire Hills." 



682 FOREST PHYSIOGRAPHY 

related to deformations acquired in three periods of folding: (i) at the 
close of the Cambrian, affecting the central portion of the area; (2) at 
the close of the Ordovician, with more far-reaching effects; and (3) in 
post-Silurian time (Devonian or Carboniferous).^ The general struc- 
tural features of the Taconic region are a succession of major and minor 
folds, as shown in the accompanying illustration. Fig. 273. These cor- 
respond approximately to the trend of the ranges. The general broad 
aspect of the structure of the Taconic Range is that of a synclinorium, 
in contrast to the geanticlinal character of the Green Mountains. The 
valleys are generally developed upon the softer limestone, the hills 
upon the harder schist.^ 

The easterly dipping cleavage of the schist determines the char- 
acter of the eastern slope of the hills. There is a marked arrange- 
ment of the drainage along north-south or longitudinal lines both 
within the range and in the bordering valleys. There are 5 main 
transverse valleys — the valley- of the Hoosic, the Mettawwe, the 
wide valley of the Walloomsac, the Battenkill, and the valley of the 
Castleton. Of these the Hoosic and the Walloomsac are deeply in- 
trenched in wide valleys and the Taconic Range is greatly dissected in 
their vicinity.^ 

The main forms of the Taconic mountains are narrow ridges of harder 
rock separated by valleys developed upon softer rock. There is con- 
siderable variation in the lengths and forms of the ridges. Some are 
long, others short. The longer ones in many cases sag gently toward 
the center in response to variations in the axial pitch of the anticlines, 
or to the exposure of softer limestones in the heart of the anticlines. 
The shorter ones are in some cases roughly pyramidal in outline, irregular 
spurs with amphitheater-like hollows between them. There is also a 
small number of plateau-like masses. Few cliffs occur though some of 
these attain heights of 1000 feet. 

The rugged hilltops and ridge tops of schist thinly veneered with 
soil have few agricultural resources and constitute areas of ultimate 
forest land. In general the valleys are deeply covered with drift and 
alluvium derived in large part from the underlying limestone. They 
are fertile and have an important agricultural population. 

The Rensselaer Plateau lies between the Taconic mountains and the 
Hudson River in Rensselaer County, New York, and extends northward 
in scattered remnants toward Castleton, Vermont. Its structural fea- 

> T. N. Dale, Taconic Physiography, Bull. U. S. Geol. Surv. No. 272, 1905, p. 48. 

2 Idem, p. 29. 

' Idem, pp. 20-91. 



NEWER APPALACHIANS 683 

tures and geographic position ally it with the Taconic mountains on the 
east. It rises from 700 to 1200 feet above the adjacent valleys and 
from 1400 to 2000 feet above sea level. Its structure is broadly syn- 
clinal, its rocks massive, and its relatively flat surface is the product of 
base-leveling. The lakes that dot its surface are chiefly due to irregular 
glacial erosion. It bears little good soil and in this respect is in marked 
contrast to the fertile Hudson Valley on the west, the Berlin and Berkshire 
valleys on the east, and even the Berkshire Hills. It was once thickly 
timbered, but has since been deforested, and is to-day an unattractive 
region with relatively steep slopes on the east, north, and south, and 
with a general westerly inclination. 

The extreme northern end of the Newer Appalachians is the St. Law- 
rence Valley, which drains out to the northeast longitudinally like the 
Coosa on the southwest. In this respect the extremities are in contrast 
to the greater part of the province, which is drained only by tribu- 
taries, the master streams crossing the mountain ridges and valleys 
alike at right angles. The limestones on the northern side of the 
St. Lawrence Valley have been weathered down into a lowland exten- 
sively covered with glacial detritus and estuarine deposits formed when 
the land stood lower than now and the sea washed the foot of strand 
lines now elevated 1500 feet above sea level. The lowland strips be- 
come narrower toward the northeast and finally disappear before reach- 
ing the mouth of the Saguenay. Beyond this point the bay of the 
St. Lawrence occupies the entire breadth of the lowland. 

Tree Growth 

The various sections of the Newer Appalachians display quite dif- 
ferent types of tree growth. The rich limestone valleys which form so 
large a portion of the southern district were originally covered with an 
excellent growth of hardwoods interspersed with open parks or natural 
prairies where the limestone is most fissured and porous and therefore 
most dry. At present the limestone valleys are extensively cleared 
owing to the exceptional fertility of their soils and the abundant supply 
of timber available on the uncultivated ridges of the province. Like- 
wise the lowland portions of the northern district are cleared and farmed. 
The zigzag ridges of the central district, on the other hand, are still for 
the most part tree covered. Their bordering slopes are quite too steep 
and their summit areas are quite too small to tempt the farmer. They 
constitute ultimate forest land of great value when kept in trees, and 
of little value, even as sheep or goat pastures, when cleared of their 



684 FOREST PHYSIOGRAPHY 

timber. The drier, sandier ridges formed on resistant sandstone, such 
as the Pocono, are marked by stunted growths of scrub pine and red 
and black oak; the more fertile valleys underlain by limestone have a 
heavy native growth of walnut, blue ash, etc. The best growth is 
found on the highest ridges of eastern West Virginia where the rainfall 
is notably greater than elsewhere in the province. 



PLATE IV 




Plate IV. — Physiographic Map of the United States. 



CHAPTER XXXII 

APPALACHIAN PLATEAUS 

The Appalachian Plateaus consist of a number of subdivisions of the 
first rank: the southern or Cumberland district; the central district in- 
cluding the so-called "mountains" of eastern Kentucky and West 
Virginia; the northern district, the Allegheny Plateau of western Penn- 
sylvania and southern New York; and the extreme northeastern por- 
tion — a special category — including the Catskill Mountains. The 
Catskills and the plateau of West Virginia and Kentucky are the loftiest 
members of the series and have truly mountainous relief and propor- 
tions. The Allegheny Plateau has been dissected into a systemless 
maze of spurs by the almost infinite branches of the deeply intrenched 
streams. The high and rugged eastern border region of the Allegheny 
Plateau is also known as the Allegheny Mountains, a term which in- 
cludes not only the Allegheny Front but also the rough uplands imme- 
diately west of it, the northern representatives of the Cumberland 
Plateau.^ Like the Cumberland Plateau the upper altitudes of the 
region represent an old erosion level, but dissection has progressed to the 
point where practically no flat land exists on the divides as an inherit- 
ance from an erosion cycle long closed. The tremendous resistance of 
the thick border rock of the Cumberland Plateau and the lower altitude 
have practically preserved it from destruction and flat uplands still 
persist. 

Northern District 

The northern district of the Appalachian Plateaus consists of the 
plateaus of western and northern Pennsylvania and southern New York 
and include such specialized tracts as the Pocono Plateau in northeast- 
ern Pennsylvania and the Catskill Mountains in east-central New York. 

The western border of the district is a well-developed scarp that 
swings southwestward along the southern shore of Lake Erie, finally 
disappearing in central Ohio. At Cleveland it stands out as a ragged 
scarp several hundred feet high, between which and the lake shore 
there occurs but a narrow strip of lowland. Farther southwest the 

1 See the Bedford quadrangle, Penn., U. S. Geol. Surv. 
685 



686 FOREST PHYSIOGRAPHY 

province has a less definite border than elsewhere except at the extreme 
south, where it descends gradually and dips beneath the Gulf Coastal 
Plain. 

Its northern border is a low ragged northward-facing escarpment 
(Fig. 275) stretching eastward from Lake Erie to the Hudson across cen- 
tral New York. The eastern end of this escarpment is formed by the 
Helderberg Mountains, where the extremely hard Helderberg limestone 
outcrops in a stratum about 500 feet thick. Farther west, in the 
Finger Lake district, the escarpment makes a bend southward, a 
change in trend due to the great thickness (1000 feet) of the soft and 



Fig. 275. — North-south section across the northern edge of the Appalachian Plateaus, Chemung River 
to Glenwood, N. Y. Vertical scale s times the horizontal. (Tarr, U. S. Geol. Surv.) 

easily eroded Salina shales. At this point too the resistant Helderberg 
limestone is only 90 feet thick. Farther west the shales thin out again, 
the sandstones and limestones become thicker, and the escarpment 
again swings back to a more northerly position. The present position 
of the escarpment is in a geologic sense merely temporary, for the 
sapping of the hard layers which are responsible for its prominence is 
going on now just as in the past. By the same reasoning it was once 
farther north than now, and has been steadily pushed southward, so that 
this part of the Appalachian Plateaus province, like so many other por- 
tions with scarped margins, is suffering a reduction in area by the 
extension of the lowlands about it. 

An interesting consequence of this process of escarpment retreat is progressive stream 
capture exhibited in many forms. The drainage of the plateau is southward almost from the 
very edge. The shorter, steeper, and more powerful northward-flowing streams are cutting 
back into the drainage systems of the Susquehanna and the Allegheny. In places they have 
diverted one tributary after another until almost the entire headwater systems of individual 
tributaries have been deflected to northerly courses. The junction of the deflected and the 
deflecting streams is marked by a sharp turn, so that the two stand in a curious relation desig- 
nated as barbed drainage. From the extent to which this feature is developed conclusions 
may be drawn as to the former position of the plateau margin in recent time. An example is 
West River above the head of Canandaigua Lake. The southward-flowing plateau streams 
whose headwaters have been captured are diminished in volume and in many cases their head- 
waters flow as tiny brooks in broad valleys. Indeed the upper portions of some valleys on the 
plateau margin are without a living stream. 

The eastern margin of the plateau of southern New York is also being pushed back rapidly 
by the short precipitous tributaries of the Hudson that descend the great scarp on the eastern 
aspect of the Catskills. Stream capture is here both vigorous and general. In places it means 
merely the westward retreat of the escarpment without sudden and great changes in the courses 
of the streams; at other places the valley sides are broken down by lateral attack, as in the 



APPALACHIAN PLATEAUS 687 

escarpment of central New York, and barbed drainage relations developed. The best-known 
case is that of the eastward-flowing Kaaterskill, which has captured the headwaters of west- 
ward- and northward-flowing Scoharie Creek and turned down a 5-miIe course waters which 
formerly flowed 50 miles to the Mohawk and down the Hudson to reach the same point. 

The plateau of northern Pennsylvania and southern New York con- 
sists of a broad elevated region so extensively and deeply dissected that 
only small remnants exist here and there of what was once a fairly 
even surface.^ The Cretaceous peneplain which by uplift became a 
plateau has by that erosion which is dependent upon uplift become a 
dissected plateau. Above its general level stand distinctly higher ridges 
with comparatively flat tops. 

The degree of dissection of this portion of the Appalachian Plateaus 
is so great that the features of the central district are repeated in kind 
though not in degree. The lesser elevation of the northern district has 
resulted in shallower valleys and a less mountainous aspect than occurs 
in eastern Kentucky, but the relief is decidedly rugged. There is the 
same kind of dependence upon the valley ways in both the newer and the 
older systems of transportation. 

"Wherever the surface is underlain by the same set of strata, it is cut into hills and val- 
leys of the same general style. One valley can not be called the counterpart of another, nor 
are the hills and uplands always alike, yet the type of topography is the same. A view from 
the top of any well-exposed upland gives a good idea of what the country is like. Below the 
upland lies a valley as variable in the nature of its slopes as it is irregular in its course. Plere 
steep walls rise from the stream on both sides. There a sharp descent on one side is faced by 
a long gentle slope on the other. Numerous ravines, some short, some long, some deep, some 
shallow, are occupied by the smaller streams which flow in from either side. As far as the eye 
can see in all directions the uplands stretch away in a broad, undulating tableland, unbroken 
by ridges, but on every hand bearing the deep scars of a multitude of valleys and ravines." - 

"Over the entire area the streams branch again and again, until there is hardly a square 
mile into which one or more has not worked its way . . . the surface is that of a well-dissected 
plateau, varying from place to place, both in elevation and in surface detail, yet everywhere 
preserving the general feature of more or less rugged relief produced by the trenching valleys 
of innumerable streams." ^ 

The topographic studies thus far made in Pennsylvania seem to show 
that three erosion levels can be identified. The first is the level of the 
ridge and hilltops in northern Pennsylvania, a feature equally well 
shown on the summits of the zigzag ridges of central Pennsylvania and 
northern New Jersey. This is the Cretaceous peneplain, and was de- 
veloped widely upon rocks of diverse structure and resistance. The 

1 M. R. Campbell, Geological Development of Northern Pennsylvania and Southern New 
York, Bull. Geol. Soc. Am., vol. 14, 1903, pp. 277-296. 

2 W. S. Tower, Regional and Economic Geography of Pennsylvania, pt. i, Physiography, 
The Central Province, The Plateau Province, Bull. Geog. Soc. Phil., vol. 4, 1906, p. 30. 

s Idem, p. 36. 



688 



FOREST PHYSIOGRAPHY 



second peneplain was early Tertiary and is known as the Harrisburg 
peneplain. It was developed upon the Chemung rocks of the northern 
part of Pennsylvania, and is also well shown in the Monongahela Valley 
on the Brownsville, Missiontown, Connellsville, and Union Town topo- 
graphic sheets, where the surface is a very gently undulating plain 
which in a distant view has an almost horizontal sky line at 1250 feet. 
The Harrisburg peneplain is best developed east of Harrisburg, where it 




Fig. 276. — Warped surface of the early Tertiary (Harrisburg) peneplain of the central Appalachians. 

(Campbell.) 



is at an altitude of 500 feet. It rises steadily upstream to about 800 
feet in the vicinity of Sunbury, and to 1200 and 1300 feet at Pittston. 
Its present warped attitude is shown in Fig. 276. 

In the Schuylkill the rocks are considerably disturbed and consist of a heterogeneous mass 
of shales; yet the hilltops are very regular indeed, with occasional monadnocks rising as high 
as 800 feet above the general 500-foot level. On the northwestern side of the Shenandoah Val- 
ley is a region of low flat-topped hills which appears like a great plain trenched by many small 
valleys. 

In the Potomac Valley (Hancock quadrangle) the Harrisburg peneplain is from 600 to 
700 feet above the sea in the southeastern corner and about 800 feet in the northwestern corner. 
The geologic structure consists of broad open folds, with many minor wrinkles, and the planes 
of stratification are generally inclined. In spite of these structural complications the peneplain 
represented by the hilltops cuts across the beds whatever their angles of inclination. 

The third topographic level is that formed in late Tertiary time; it 
is known as the Somerville or the Worthington plain. In New Jersey 
it was developed on the rocks of the Kittatinny Valley and on the 
wide outcrop of Triassic rocks which form the lowland belt across New 



APPALACHIAN PLATEAUS 



689 



Jersey and Pennsylvania, Fig. 276. It is, however, of exceedingly local 
development, and along the Susquehanna Valley as at Harrisburg it 
stands at an altitude of 400 feet, at Lancaster at 350 feet, and on the 
Potomac River near Harpers Ferry at 500 feet. It represents a partial 
cycle only, and nowhere was developed extensively across rocks of differ- 
ent hardnesses, but was etched out upon the softer formations only. 



WORTHINGTON PENEPLAIN 




Fig. 277. — The upper section illustrates the terraces of the Ohio Valley, the lower the terraces of the 
Allegheny Valley. (Top. and Geo!. Surv. of Penn.) 



In the uplift of the third and lowest plain to the present level there 
was one main halt which permitted the development of broad valleys. 
Fragments of these valleys now occur as benches along the valley mar- 
gins. All these features as well as those related to the glaciation of the 
region on the north are shown in Fig. 277. 

Among the more prominent effects of glaciation was the development 
of an extensive system of abandoned channels whose origin was long in 
doubt. They are of widespread occurrence in western Pennsylvania, 
West Virginia, and eastern Kentucky. Detailed surveys and studies 
in recent years have at last supplied a basis for an acceptable explana- 
tion.^ The abandoned channels appear to have been upbuilt by the 
streams during a period of stream aggradation associated with the 
waning stages of glaciation. All the southward-flowing streams heading 
in the glaciated country were so abundantly supplied with material that 
they aggraded their valley floors. The northward-flowing streams join- 
ing the southward-flowing aggrading streams were therefore compelled 
to aggrade their courses to the same level. In many cases they developed 

1 E. W. Shaw, High Terraces and Abandoned Valleys in Western Pennsylvania, Jotir. 
Geol., vol. 19, 191 1, pp. 140-156. 



690 



FOREST PHYSIOGRAPHY 



courses to one side or the other of the older courses, crossed low points 
in former upland spurs, and now exhibit most striking anomalies with 

respect to earlier channels. Typical con- 
ditions are represented along the Monon- 
gahela and its tributaries, as shown in 
Fig. 278. 

POCONO PLATEAU 

The Pocono Plateau, a separate division 
of the northern district, lies in the north- 
eastern corner of Pennsylvania, almost 
completely separated from the rest of the 
plateau areas of that state by the deep 
synclinal trough of the Wyoming Val- 
ley. The Pocono Plateau covers Monroe, 
Pike, Wayne, and eastern Carbon counties, 
merges southwestward into the ridge area 
of the anthracite coal region, and extends 
east and north to become the Catskill Pla- 
teau of New York state. Almost the 
whole of it is underlain by the broad 
strata of nearly horizontal hard sandstone 
and conglomerate at the bottom of the 
Coal Measures series. 
The southern edge of the plateau is often 
known as Pocono Mountain and presents a close analogy to the Alle- 
gheny front, both in origin and in character. It is an erosional 
escarpment, 1000 feet high, with a step-like ascent resulting from the 
horizontal position of the strata. The plateau back of the boundary 
escarpment (Pocono Mountain) is a nearly level upland wilderness, 
known to the early settlers as the "Great Beech Woods" and the 
"Shades of Death." Over most of its extent it stands from 1400 to 1800 
feet above the sea. Below this level the streams have cut valleys from 
100 to 200 feet deep, and an occasional knob rises 200 or more feet above 
the upland. It is often described as one of the wildest parts of the 
state, "a wilderness of forest and swamp," but it is made picturesque 
by the numerous lakes and cascading streams that are the result of the 
glacial action to which the region has been subjected. '- 




Fig. 278. — Present and pre-Pleistocene 
courses of Monongahela (left) and 
Youghiogheny rivers. (Top. and 
Geol. Surv. of Penn.) 



' W. S. Tower, Regional and Economic Geography of Pennsylvania (Physiography), Bull. 
Geog. Soc. Phil., vol. 4, 1906, pp. 216-217. 



APPALACHIAN PLATEAUS 691 

CATSKILL MOUNTAINS 

The Catskill Mountains stand upon the northeastern border of the 
Appalachian Plateaus as a conspicuous group of ridges and peaks of 
mountainous proportions. Their summits reach to heights almost 
double those of the adjacent plateau. Some of the principal peaks are 
Slide Mountain (4220 feet), Hunter Mountain (4052), Black Dome 
(4000), Windham High Peak (3809), etc. From, the upper portions 
of the Hudson Valley their whole elevation may be seen in a single view, 
from which point they appear to have imposing form and height. The 
blue haze that generally hangs over them — a feature of rare beauty 
in autumn weather — lends to their height a majesty and to their out- 
lines a softness which in a distant view blend to form one of the most 
charming sights of the Atlantic slope. 

The structure of the Catskills is as simple as that of the neighboring 
plateau on the west. The strata lie almost fiat, with slight dips to 
the west, northwest, and southwest in various places. Anticlinal and 
synclinal structures are practically absent, and even when present they 
trend not with the ranges of the Catskills but at right angles to them, 
showing no relation to the present topographic forms. Shale com- 
monly outcrops on the lower slopes of the valleys, but sandstones occur 
higher in the section, and on the summits of the principal peaks the 
rock is generally a conglomerate, very durable and thick. The flatness 
of the strata is expressed in the fiat summits of the mountains, a 
characteristic feature and one that often interferes with the view, since 
these mountains are all heavily wooded. The tops are often of consider- 
able extent and are never sharp-pointed peaks as in a region of alpine 
forms. While the valleys among the mountains are broad and open their 
sides are often cliffed to a notable extent for some distance. This is due 
to the system of almost vertical joints, which are the principal lines of 
weakness along which secondary erosion and valley widening take place. 
Abrupt ledges are frequent and are often a source of great difi&culty in 
ascending a peak by unusual paths. In a few places these ledges are 
of great height and afford splendid panoramas over the surrounding 
country, as at the Catskill Mountain House and Overlook Mountain. 
To the vertical jointing and erosion along the joints is also to be at- 
tributed the successive steps which are common features of the valley 
floors and give rise to numerous picturesque cascades. 

There are two main ranges in the Catskills, the line of division being 
marked by Esopus Creek. The southern Catskills consist of a massive 
central chain which bears the highest mountain in the Catskills, Slide 



692 FOREST PHYSIOGRAPHY 

Mountain. The roughness of the topography and the unbroken forest 
that covers the mountain makes the penetration of this part of the 
Catskills very difficult. The northern ranges of the Catskills trend 
northwest and the principal range is about 35 miles in length. It makes 
a sharp curve, bending back upon itself in a sort of secondary range. 
A number of lateral spurs or secondary ranges trend at right angles to 
the main ones. Toward the south and southwest the main range falls 
off in long slopes and heavy spurs. It is divided into four sections by 
three deep gorges or " cloves " which give access to the interior valleys. 

The drainage of the Catskills is chiefly to the 'west by tributaries of 
the Scoharie system. This appears to be a consequent drainage de- 
veloped upon the original surface at the time of uphft of the region. 
Base-leveling, which is so common a feature of the Appalachian Plateaus, 
appears to be absent here; the Catskills appear to have survived as 
residuals because of their original superior height and the protection of 
the heavy cap of horizontal conglomerate. Erosion produced important 
effects, however, and opened up the broad valleys that are character- 
istic of the region. A common feature of the valleys is the presence of 
a pronounced shoulder halfway up the valley slopes, a feature which 
appears to be related to later uplift and dissection in the Tertiary. 
Were the valleys filled almost to the level of the shoulder we should 
probably have a picture of the Catskills as they appeared at the close of 
the Cretaceous cycle of denudation. They would then present smooth 
flowing outlines without any important number of steep ledges; the 
latter are commonly found below the level of the shoulder, where vigor- 
ous erosion is now taking place. The effects of Tertiary erosion are 
also shown in the form of local lowlands of limited extent opened up 
here and there within the mountain borders. 

Although the Catskills were overridden by ice, signs of which are 
everywhere abundant, the ice appears not to have had any important 
effect upon the topography; rather it conformed to the broad slopes, 
only slightly molding them here and there by the deposition of small 
quantities of glacial till or by the erosion of the sharper forms. ^ 

SOILS AND VEGETATION 

The most uniform type of soil in the glaciated northern portion of 
the Allegheny Plateau is the till sheet which veneers the hills and up- 
lands. It is a smooth, thin, and locally stony sheet of bowlder clay. 

• For an excellent topographic description from which the above is largely derived see 
Arnold Guyot, On the Physical Structure and Hypsometry of the Catskill Mountain Region, 
Am. Jour. Sci., 3d Series, vol. 19, 1880, pp. 429-451. 



APPALACHIAN PLATEAUS 



693 



The soil is much deeper in the valleys and of more variable form and 
composition, especially where morainic accumulations occur side by 
side with fluvio-glacial material — ^kames, eskers, outwash plains, and 
the like. In both the uplands and the valleys a large proportion of the 
glacially derived material is from underlying shales which weather into 
clay and increase the fertility of the soil by increasing its water-holding 
capacity. The varying proportion of this soil element causes great 
variation in the rapidity and thoroughness of soil drainage, so that in a 
dry spell one part of a field may be covered with a fresh green growth 
while another part near by may be parched and brown. ^ Swampy tracts 




.Fig. 279. — Distribution of morainal deposits and direction of ice movement in western New York. 

(Tarr, U. S. Geol. Surv.) 



are characterized by a fertile black muck of great value when drained. 
Besides these soil types are narrow strips of flood-plain deposits and 
fan-shaped alluvial accumulations where the hill streams descend 
abruptly to the main valley floors. 

While practically none of the primitive forest can now be found in 
the region, yet the uplands and valley slopes, too steep for cultivation, 
are in the main covered with extensive forests. The forest cover is 
extending naturally and encroaching on the cleared lands. The thin, 
stony upland soils are relatively infertile, and the extension of the forest 

1 R. S. Tarr (Williams, Tarr, and Kindle), Watkins Glen-Catatonk Folio U. S. Geol. Surv. 
No. 169, 1909, p. ss. 



694 FOREST PHYSIOGRAPHY 

over them would benefit the region not only from the standpoint of 
forest products but also from that of the agricultural interests of the 
valleys, which suffer from increasingly destructive floods.^ 

Central District 

The central district of the Appalachian Plateaus lies in eastern Ken- 
tucky and West Virginia and is the ruggedest portion of the entire prov- 
ince. The highest portions are from 3000 to 4000 feet above sea level 
and are known locally as mountains, a name they fully deserve. The 
eastern rim of the district in Kentucky is Pine Mountain, whose steep 
eastern escarpment rises from 800 to 1500 feet above the Great Valley 




Scale of Miles 
Fig. 280. — Maturely dissected Allegheny Plateau in West Virginia. The large depression on the right 
is the valley of the Kanawha at Charleston. Note the prevalence of slopes and the absence of flat 
land. 

on the east and has but one water gap in 150 miles. The Kentucky 
''Mountains" are structurally a part of the Cumberland Plateau and 
formerly had a flattish simimit; the original nearly flat surface has 
been so greatly dissected however that but few remnants remain to in- 
dicate the former level. These, however, show a remarkable uniformity 
of elevation on northeast-south vvest lines, so that the eastern escarp- 
ment of the district has an almost perfectly straight sky line. 

The western slopes of the district are in sharp contrast to the eastern. 
There is a bordering escarpment, but it is highly irregular, the streams 
having carved valleys far back into the elevated portions of the upland, 
leaving long narrow spurs running out toward the west. The valleys 
are steep and gorge-like; the main streams such as the Kanawha occupy 
canyons; flat land is seldom found to any extent either upon the hill sum- 
mits or on the valley floors. It is a hili-and- valley country. Fig. 2 So, where 
so little flat land occurs that the water everywhere falls upon a slope 
and the run-off is heavy; floods due to spring rains and the melting of 
late winter snows are common and rise to great heights in the confined 
valleys, destroying roads and bridges, washing away the valley soils 
or covering the soils of the narrow flats or flood plains with heavy 
deposits of coarse waste. Almost all the roads and trails follow the 
valleys, to which the railroad lines themselves are strictly confined. 

1 R. S. Tarr (Williams, Tarr, and Kindle), Watkins Glen-Catatonk Folio U. S. Geol. Surv 
No. 169, 1909, p. 33. 



APPALACHIAN PLATEAUS 695 

Travel by any means is often suspended during time of high water. 
The whole section is a great forested wilderness whose resources of coal 
and timber constitute its chief wealth, resources slow in development 
because of the almost insuperable topographic obstacles to transporta- 
tion. Even the railways on the margin of the country have been built 
since 1880. 

Magnificent forests once covered the central district of the plateau 
region. They are still untouched in the remoter localities. Oak, wal- 
nut, poplar, chestnut, maple, ash, and tulip trees grow to great size. 
The making of staves of white oak is a considerable industry among an 
isolated and backward mountaineer folk. Since the roughness of the 
country limits the railways to the principal streams, the lesser water- 
ways are almost everywhere utilized for rafting both timber and lumber 
to the railroads and the lowlands. In many sections remoteness from 
transportation lines forbids any attempt at forest exploitation. As in 
the southern Appalachians a wasteful system of agriculture is practiced. 
Hillside farms are cleared of the finest timber by combined girdling 
and later burning, then cultivated a few years and abandoned for a new 
site. The abandoned clearing grows up to useless brush or is deeply 
gullied and the thin soil washed away.^ 

Southern District 

cumberland plateau, walden ridge, lookout mountains, etc., 
and the highland rim 

A first inspection of the flat-topped plateaus of the southern district 
leads one to the conclusion that the flatness is a function of the struc- 
ture, for the strata appear to have a roughly horizontal attitude. A 
closer examination, however, reveals the fact that the plateau surface 
does not generally coincide with a particular stratum however resistant 
it may be; the surface is found to be composed of very soft shale as 

1 For extremely interesting and accurate descriptions of both the physical geography of 
the region and the Kentucky mountaineers see the writings of John Fox, Jr., as for example 
Hell-fer-Sartin, Blue Grass and Rhododendron, and The Trail of the Lonesome Pine. On 
Horseback to Kingdom Come, Scribner's Mag., vol. 48, No. 2, igio, p. 175, discusses later in- 
dustrial development. The best scientific description of the country and the people is by E. C. 
Semple, The Anglo-Saxons of the Kentucky Mountains, A Study in Anthropogeography, 
Geog. Jour., vol. 17, 1901, pp. 588-623. In Theodore Roosevelt's The Winning of the West 
(The Spread of English-speaking Peoples), vol. i, ed. of 1905, pp. 146-147, is a fascinating de- 
scription of the forest of pioneer days. For a good topographic description of portions of 
eastern Kentucky see Ky. Geol. Surv., vol. 5, n. s., 1880. For a discussion of the natural 
water routes of the Kentucky mountains see N. S. Shaler, The Transportation Routes of 
Kentucky and their Relation to the Economic Resources of the Commonwealth, Ky. Geol Surv., 
vol. 3, pt. 5, 2d series, 1877. 



696 FOREST PHYSIOGRAPHY 

well as of very hard sandstone. In short, the surfaces of the various 
plateaus truncate hard and soft beds and are much more nearly hori- 
zontal than the strata upon which they have been developed.' 

Following the principles we have already applied so frequently in the 
study of the physiography of the United States, we shall conclude 
that the surfaces of Walden Plateau, Cumberland Plateau, Lookout 
Mountain, Sand Mountain, etc., are portions of an uplifted peneplain in 
process of more or less rapid dissection. Along certain lines narrow 
anticlinal folds had developed during the period of structural deforma- 
tion, with broad synclines between. The projection of the anticlines 
above the level of the peneplain resulted in their erosion and the ex- 
posure of softer underlying beds lying in the heart of the anticlines. 
When later uplift occurred, opportunity was afforded for the dissection 
of the softer exposed beds. The result has been that the synclinal 
basins of an earlier period have been converted into the mountains and 
plateaus of the present period. 

One of the most important departures from the plateau topography is 
known as the Sequatchie Valley, which separates Walden Plateau from 
Cumberland Plateau. It lies parallel with the Great Appalachian 
Valley, has remarkable continuity and regularity of expression for over 
100 miles, and appears to be an outlying anticlinal fold of the Appa- 
lachian system of folds. 

The Sequatchie anticline, like the anticlines of the Newer Appalachians, has a typically 
unsymmetrical form, the beds dipping much more steeply on one side of the axis than on the 
other, and the gentler dips are upon the eastern side. Near the upper end of the Sequatchie 
Valley the strata have been broken by a thrust fault developed along the steep side of the 
arch. Walden Plateau on the east shows a distinct synclinal structure. Of similar structure 
is Lookout Mountain, but it is much narrower than Walden Plateau. Wills Valley, developed 
upon an anticline, separates the syncline of Lookout Mountain from the syncline of Sand 
Mountain, and Sand Mountain is in turn separated from Cumberland Plateau by the valley 
of Tennessee River, which has been developed in the southwestward extension of the Sequatchie 
anticline. 

Along the eastern edge of Cumberland Plateau the strata dip west- 
ward at a steep angle, but these dips are maintained for very short 
distances, usually not more than a few rods, where they change to dips 
that are sensibly flat, a condition maintained across the Cumberland 
Plateau and the Highland Rim. Though apparently horizontal the beds 
dip toward the southeast from 20 to 30 feet per mile. 

It must not be supposed that Cumberland Plateau and Walden 
Plateau were perfectly peneplaned. Along the western edge of Walden 
Plateau, the northern end of Lookout Mountain, the eastern edge of 
Cumberland Plateau, and at a large number of isolated points elsewhere, 



APPALACHIAN PLATEAUS 697 

residuals in the form of isolated knobs or mesas rise from 100 to 300 
feet above the general level of the plateau. In places, the residuals are 
composed of more resistant beds of massive conglomerate, but the resid- 
uals within the borders of the plateaus are composed of horizontal 
strata in some cases capped by a bed of conglomerate but more often 
composed entirely of rather soft sandstones and shales. 

Following the uplift of the Cretaceous peneplain there ensued a period 
of crustal stability sufhciently prolonged to enable the forces of erosion 
to develop a partial peneplain at a level from a fev/ hundred to a thou- 
sand feet lower than the Cretaceous. The peneplanation accomplished 
during this period was chiefly upon the softer rock of the region and 
was so incomplete as to leave large portions of the Cretaceous peneplain 
standing above the early Tertiary peneplain in the form of massive 
unakas, as shown in Fig. 238. The early Tertiary peneplain is called 
the "Highland Rim" peneplain because the Highland Rim, so-called, 
between the Nashville basin and the Cumberland Plateau, is the best- 
preserved portion. 

As in the case of the well-preserved remnants of the Cretaceous peneplain, the remnants 
of the early Tertiary or Highland Rim peneplain have been preserved largely because of the pres- 
ence of resistant beds along the outer margin, but the peneplain as a whole truncates beds of 
widely differing degrees of resistance to erosion. The peneplain is preserved upon rocks of 
intermediate resistance, chiefly siliceous limestones and sandy shales, for rocks of greater re- 
sistance than these were never base-leveled, and rocks of less resistance were dissected in the 
uplift which closed the early Tertiary cycle of erosion. 

The elevation of the Highland Rim peneplain is about 1000 feet, west 
of the Cumberland Plateau in the Appalachian Valley it is about 11 50 
feet, toward the northern edge of the Chattanooga district 950 feet. 
Elevations above the topographic level developed on the Highland Rim 
are in the form of isolated residuals similar to those we have noted upon 
the Cumberland Plateau, as long irregular projecting spurs along the 
ragged west border of the Cumberland Plateau, or as massive unakas 
such as Cumberland and Walden plateaus themselves. 

On the western and southern borders of Cumberland Plateau many 
long spurs and isolated knobs, products of circumdenudation, project 
irregularly westward over the surface of the Highland Rim, breaking the 
continuity of the eastern portion. Between the spurs are great gorges 
from 800 to 1000 feet deep, which, on account of their depth and 
narrowness, are known as "gulfs." At their heads coves are found, 
headwater alcoves which usually contain a pocket of limestone soil that 
supports a better timber growth than the flat upper surfaces of the 
upper and lower plateaus with their thin soils formed upon sandstones 



698 FOREST PHYSIOGRAPHY 

and shales. Both the distribution of the soils and the character of the 
topography on the border of the Cumberland Plateau are due to the 
structure. 

Between the hard sandstone and conglomerate capping most of the Cumberland Plateau 
and the rock of the lower country about it are soft limestones and shales which are so easily 
eroded as to result in the sapping and undermining of the hard formations above them. It is 
this process which maintains the steepness of the border scarps (especially their upper portions, 
which are frequently vertical cliffs) and results in the sharp line of delineation between the 
Appalachian Plateaus on the one hand and the Appalachian Valley and Highland Rim on the 
other. These features are persistent, being found on the projecting portions of the plateau as 
well as at the heads of the coves.i 

The "barrens" of Tennessee are developed chiefly upon shales 
(Waverly) which yield a white, siliceous, and unproductive soil; Scarcely 
more productive are the soils derived from sandstones which are thinly 
inhabited and have thin native forests of pine and oak. The surface 
of Cumberland Plateau, consisting of sandstones and shales, is covered 
with a thin poor soil; the Highland Rim is also far from having a pro- 
ductive soil, though on its western margin, where a limestone (New- 
man) outcrops, a soil of greater but not of high fertflity occurs. In 
general the timber covering of the flat plateau summits and remnants is 
thin, but in the coves, hollows, and gorges, where a richer soil and more 
abundant water supply are found, hickory, chestnut, and oak reach a 
good size and grow in first-class stands. Near the watercourses, pine, 
hemlock, and spruce find the necessary demerits of their environment, 
but their growth is everywhere second in importance to the members 
of the first-named series." 

LIMESTONE SOILS OF THE APPALACHIAN VALLEYS 

"The limestone soils are among the most extensively developed of any in the United States 
and occur in both broad upland and enclosed narrow valley areas. The greatest upland de- 
velopment is seen upon the Cumberland Plateau in eastern Tennessee and Kentucky and 
upon the Carboniferous formation in central Tennessee and Kentucky, northern Alabama and 
Georgia, and in Missouri. The valley soils are found principally in Pennsylvania, Maryland, 
and Virginia, and in the mountain section of eastern Tennessee and Kentucky and northern 
Alabama and Georgia." 3 

The limestone soils are residual in origin, being derived from the 
weathering in place of limestone of several ages and variable composition. 
This is accomplished by the removal through solution of the calcium car- 
bonate of the limestone. Limestone soils are remarkable for the fact 

1 C. W. Hayes, Seuanee Folio U. S. Geol. Surv. No. 8, i8g4, p. i. 

2 A. Keith, Wartburg Folio U. S. Geol. Surv. No. 40, 1897, p. 4, col. 3, and M. R. Campbell, 
Standingstone Folio U. S. Geol. Surv. No. 53, 1899, pp. 4-5. 

' Soil Survey Field, Book, U. S. Bur. of Soils, 1906. 



APPALACHIAN PLATEAUS 



699 




c o 
2 O 

M . 
u 13 



55 ^ 



T3 p 



I 6 



7CO FOREST PHYSIOGRAPHY 

that they constitute but a small percentage of the original limestone 
rock, the larger part having gone into solution, leaving behind the more 
resistant siliceous minerals. It has thus required the solution of many 
feet of rock to form a foot of soil. They have a naturally heavy charac- 
ter. Solution and subsequent filtration of pure massive limestone of 
Cambro-Silurian age have given rise to a soil which as a rule occurs in 
valleys bordered by areas of the more resistant sandstones and shales. 
The series is typically developed in the limestone valleys of the 
Great Appalachian Valley and in the central basins of Kentucky and 
Tennessee, but smaller areas are found as marginal deposits in the 
Piedmont section and in the deep valleys of the Appalachian Plateaus, 
where the underlying limestones have been exposed to weathering by 
deep erosion. The most productive valley phase occurs iii the Great 
Appalachian Valley. 

The cherty and fossiliferous limestones (St. Louis) of the region have 
given rise to a second soil type which occurs on both the level and the 
undulating uplands and in rough, hilly country with steep valleys. 
Where the latter features predominate the soils are generally unpro- 
ductive and very stony, but in some sections are adapted to fruit, 
especially apples. The soils formed from beds of purer limestone occu- 
pying level and gently rolling areas are as a rule very productive. 

Local Lowlands^ 

blue grass and nashville basins 

The upland quality of the general regional slope of the Appalachian 
Plateaus is interrupted in Kentucky and Tennessee by lowlands of 
unusual size and importance. The Kentucky lowland is the Blue 
Grass country, famous for its rich limestone soils and its nutritious 
blue grass; the Nashville lowland or Central Basin is of equal impor- 
tance, though it has for some reason never gained such general renown. 
In respect of soil fertility and easy cultivation both are in happy con- 
trast to the uplands about them, which are as a whole either too broken 
to permit easy tillage or too thinly covered with soil of inferior quality 
to tempt men in large numbers. These two lowlands are essentially 
alike in structure and origin in spite of many detailed differences. 
Both are great structural domes which extended above the general 
level of the surface of erosion once developed here. The Blue Grass 
lowland was developed in the early Tertiary cycle of erosion and was 
so denuded by the base-leveling of that period as to have its cap rock 
either partially or wholly removed. With later uplift, erosion quickly 



APPALACHIAN PLATEAUS 701 

cut below the hard and into the underlying soft strata, Plate V and 
Fig. 282. The result was a lowland, while the surrounding areas, under- 
lain by the hard strata once arching over the dome, remained as uplands. 
The central basin of Tennessee or Nashville Basin was developed in the 
late Tertiary cycle of erosion under similar conditions. 

BLUE GRASS COUNTRY 

The general altitude of the Blue Grass country of north-central Ken- 
tucky is from 800 to 1000 feet above sea level. The region may be 
described as a broad plain on whose southern margin the hills rise 
abruptly; in the hill country the large streams have cut deep narrow 
gorges which only become slightly less deep and narrow throughout the 
Blue Grass region itself. Although in short distances the surface of this 
plain appears to be structural and to correspond with the bedding of 
the limestone rocks (Ordovician) which compose the greater part of the 
surface, a large view discloses the fact that the surface cuts across 
rocks of different ages and varying degrees of hardness, and is an up- 
lifted peneplain, called the Lexington peneplain.^ 

The hills which rise above the Lexington peneplain have a fairly constant altitude of about 
1500 feet. They generally have round or sharp tops and a regular altitude despite the varia- 
tion of the underlying rock, hence it is inferred that they too represent a former peneplain, the 
Cretaceous peneplain of the Appalachian region. 

It is noteworthy that the valleys of the Lexington peneplain of the 
Blue Grass region exhibit a topographic unconformity showing two epi- 
sodes of erosion. Long gentle slopes lead down from the surface of the 
Lexington peneplain to an inner valley with steep walls. The gentle 
slopes evidently constitute the borders of an older broad valley in the 
bottom of which the modern narrow gorge has been cut. The floors of 
the older valleys bear deposits of sand, while the sides of the modern 
valleys are in many cases rock cliffs. ^ 

The Blue Grass country of Kentucky is developed upon a broad struc- 
tural arch known as the Cincinnati anticline, which extends from Nash- 
ville through Lexington, nearly to Cincinnati. Its occurrence north of 
the latter point will not be described here, for it is of lesser topographic 
importance than glaciation which has largely concealed it. The Cincin- 
nati arch south of Cincinnati may be divided into two broad domes, one 
of which culminates near Nashville, Tennessee, and the other in Jessamine 
County, central Kentucky.^ 

1 M. R. Campbell, Richmond Folio U. S. Geol. Surv. No. 46, 1899. 

2 Idem. 

3 G. C. Matson, Water Resources of the Blue Grass Region of Kentucky, Water-Supply 
Paper U. S. Geol. Surv. No. 233, 1909, pp. 26-27. 



702 



FOREST PHYSIOGRAPHY 



A large part of the Blue Grass region, and particularly that part of it 
in Woodford, Franklin, and Fayette counties, Kentucky, has fiat-topped 
divides with practically no surface drainage. This condition furnished 
exceptionally favorable opportunities for the formation of caverns and 
the development of underground drainage systems for which Kentucky 
is noted. The topography is marked by a series of sink holes which 




HORIZONTAL SCALE OF MILES 



^TrentoD LimeetoDe 



SECTION SHOWING GEOLOGICAL STRUCTURE 

OF 

WESTERN OHIO AND EASTERN INDIANA. 



j Niagara Limestc'ne . 
Niagara Shale E 

Clinton Limestone 



Fig. 282. — Northern portion of the Cincinnati arch, showing exposure of the lower and softer beds of 

shale and limestone. 

receive a large part of the rainfall. It is inferred that before the uplift 
of the Lexington peneplain so large a part of the surface was drained by 
underground streams that surface drainage was probably limited to the 
larger streams and their principal tributaries.^ The sink-hole topography 
of the Blue Grass region favors the quick removal of surface water and 
Its rapid absorption by the rock.^ 

The residual soils of the Blue Grass region range in thickness from 3 to 
5 feet on the average, but with extreme ranges from a few inches up to 
about 30 feet. The residual material absorbs and stores the rainfall 
and delivers it gradually to the underground channels. Were the rock 
surface exposed, springs would flow only a short time after each rain, 
and the stream flow would be exceedingly irregular.^ 

The Blue Grass region has been famous for its excellent soils ever 
since the first settlers under Daniel Boone penetrated the region. 
The finest types of soils occur where the Lexington Hmestone is from 
140 to 160 feet or more thick. It is composed of bluish finely crys- 
talline Hmestone in thin irregular beds frequently separated by in- 
tervals of calcareous shale.^ The soils of the Lexington limestone are 
loamy. 

■ G. C. Matson, Water Resources of the Blue Grass Region of Kentucky, Water-Supply 
Paper U. S. Geol. Surv. No. 233, 1909, p. 30. 
^ Idem, p. 60. 
3 Idem, p. 62. 
* M. R. CampbRll, Richmond Folio U. S. Geol. Surv. No. 46, 1899, p. j. 



APPALACHIAN PLATEAUS 703 

The upland soil of the Blue Grass region is adapted to a large variety 
of crops such as blue grass, corn, wheat, tobacco, and hemp. In the 
Ohio Valley occur small areas of loam which are well adapted to general 
farming, but they do not equal the upland areas either in extent or in 
value. The purest soils of the region are those derived from the Eden 
shale, which usually occupies the hilly areas. It is subject to rapid 
erosion because of its softness, and in many places attempts to farm this 
soil have been abandoned and it has been converted into pasture and 
timber. 

It is not always the case in the Blue Grass region that each rock for- 
mation yields a distinctive type of soil. It has been found that a soil 
derived from a calcareous shale may be little different from one de- 
rived from a clayey limestone. The large amount of limestone dis- 
solved to form the soils of the Blue Grass region naturally means that a 
certain amount of carbonate of lime is found in the soils to-day, which 
gives it a slight tendency toward aggregation into soil crumbs. The 
analyses show that the sizes of the openings between the crumbs of the 
Blue Grass soils are very small and that the soils have great capacity for 
retaining moisture. The small size of the pores also brings the ground 
water into contact with a large amount of soluble material and favors 
the solution of the various elements of plant food. Chemical analyses 
of the Blue Grass soils show that the plant elements are so abundant in 
them that it is generally unnecessary to add fertilizers. The average of 
32 analyses of soils from the Lexington limestone is represented in the 
following table. 

AVERAGE COMPOSITION OF SOILS FROM LEXINGTON LIMESTONE 

Per cent 

Organic and volatile matters 6. 211 

Alumina, iron, and maganese oxides 11.200 

Lime carbonate -749 

Magnesia -644 

Phosphoric acid (P2O5) 328 

Potash extracted by acids -404 

Sand and insoluble silicates 73-38o 

Another feature of these soils that gives them a high degree of fer- 
tility is the large quantity of phosphorus contained in them in the 
form of phosphate of lime derived from Ordovician limestones. They 
are richer than' the average in those mineral elements which support 
plants.^ 

The low productivity of the soils developed upon the Ohio shales is 

1 G. C. Matson, Water Resources of the Blue Grass Region, Kentucky, Water-Supply 
Paper U. S. Geol. Surv. No. 233, pp. 33-35- 



704 FOREST PHYSIOGRAPHY 

to be attributed not to a deficiency in the elements of plant food, but 
to an excess of moisture. They are so clayey that they retain too 
large quantities of rainfall and tend to remain wet and sour.^ 

NASHVILLE BASIN (CENTRAL BASIN OF TENNESSEE) 

From the steep and ragged western escarpment of the Cumberland 
Plateau the country extends westward as a more or less deeply dis- 
sected plateau about looo feet above sea level, known as the Highland 
Rim. This in turn terminates on the west in an escarpment which 
practically surrounds a lowland known as the Central Basin of Ten- 




Fig. 283. — Section across the Nashville Basin of Tennessee and the country adjacent, from the Cumber- 
land Plateau (right) to the Harpeth River. C, Cambrian; Ot, Trenton limestone; On, Nashville 
shale; Sn, Niagara limestone; Db, Berea shale; Ms, sandstone; Mlm, Mountain limestone; C, Coal 
Measures. Lengthof section about 120 miles. (Safford, Geol. of Tenn.) 

nessee. It is about 70 miles across, extends north and south about 60 
miles, and stands about 600 feet above sea level. It is drained by the 
Tennessee and its tributaries through a narrow gorge-like valley that 
cuts through the surrounding uplands. It has a gently undulating 
surface save on the border, where spurs from the surrounding plateau 
and isolated hills, which represent detached and greatly eroded spurs, 
occur in numbers. The deeper and richer soils of the basin, its low- 
land character, and its relation to the surrounding uplands that stand 
about 400 feet above it, give it a distinctive character. These features 
all rest back upon the structure and late physiographic development 
of the region. 

The present lowland was originally an upland with respect to sur- 
rounding tracts. This relation was owing to its domed structure, the 
rocks dipping outward in all directions though at varying rates. Dur- 
ing the erosion cycle in which the Highland Rim w^as formed (early 
Tertiary) the topographic effects of the doming were obliterated and 
the cap rock, a cherty limestone, reduced in thickness because of its 
domed attitude. The base of the formation was, however, below the 
plane of base-leveling, hence the formation, though thinned, was not 
broken through at any point. 

1 For the soils of this region see R. Peter, Comparative Views of the Composition of the 
Soils, Limestones, Clays, Marls, etc., of the Several Geological Formations of Kentucky, etc., 
Geol. Surv. of Ky., 1883. 



APPALACHIAN PLATEAUS 705 

The early Tertiary erosion cycle was interrupted by uplift which en- 
forced dissection. Soon the intrenched streams cut through the thin 
cherty limestone capping the dome, but were not able elsewhere to 
breach the formation because of its greater thickness. The underlying 
limestones are free from chert, are soft, shaly, and easily eroded, and 
were worn down to a lowland while the surrounding country capped 
by the hard cherty formation maintained its level. Though the whole 
Highland Rim is more or less dissected, considerable areas of dissected 
remnants occur which preserve the ancient level; in the lowland no 
trace of the ancient level remains except on the margins. After the 
development of the lowland there occurred two later uplifts of the land. 
After the first uplift the valleys were broadly opened several hundred 
feet below the general level. The second uplift caused the streams to 
cut narrow valleys within the broad ones, leaving the remnants of the 
broad valleys as terraces along the upper levels of the lower valleys. 
The descent from the lowland to any valley floor is over a terrace which 
marks a topographic unconformity or break between a younger and 
lower and an older and higher set of slopes. 

In the Nashville Basin the soil characters are very intimately related 
to the underlying geologic formations. The conditions in the Colum- 
bia district in the southwestern part of the basin are typical. The 
former great red-cedar glades of middle Tennessee were here formed 
upon the Lebanon limestone, which has a shallow and rocky but fertile 
soil. The purest soil of the region is derived from a cherty shale and 
limestone known as the Tullahoma formation, which is flinty and nearly 
always occurs on steep slopes. When thoroughly leached and light in 
color it constitutes the "barrens" of the Highland Rim. If the for- 
mation is underlain by clay so that the calcareous matter can not be 
readily leached out, the soil is very good and capable of producing abun- 
dant crops. A number of good soil makers have a limited outcrop or out- 
crop on steep slopes where the soil is readily washed away, and are of 
little importance to vegetation. Among the best of natural blue-grass 
soils in the Nashville Basin is the Bigby limestone, which is a crystalline 
phosphatic limestone from 30 to 100 feet thick in the Columbia region.^ 

The surrounding uplands, or the Highland Rim, have a thinner and 
less fertile soil. Toward the north the upland is underlain by sand- 
stone, and here occur the famous " barrens " of Kentucky and Tennessee, 
long without more than a mere sprinkling of agricultural population. 
The first settlers in Kentucky also regarded the untimbered limestone 
lands of the western part of that state as infertile, and gave them the 

• Hayes and Ulrich, The Columbia Folio U. S. Geol. Surv. No. 95, 1903, p. 6. 



7o6 FOREST PHYSIOGRAPHY 

name of "barrens" from their previous experience of the relative in- 
fertihty of untimbered lands. Several years passed before the true 
character of these "barren lands" was ascertained and their fertility 
recognized.'^ So, too, the sandstone barrens to the east of the lowlands 
have had their day of neglect, but are now cultivated to an increasing 
degree, and when properly fertilized yield profitable though not as a 
rule abundant harvests. On steep slopes they are too thin and culti- 
vation is mechanically too difiScult, and such belts along stream valleys 
are commonly left timbered; the interfluves are formed on gentler slopes 
and have a deeper though rarely a fertile soil. 

' N. S. Shaler, The Origin and Nature of Soils, 12th Ann. Rept. U. S. Geol. Surv., pt. i, 
1890-91, p. 325. 



CHAPTER XXXIII 

LOWLAND OF CENTRAL NEW YORK 

The most noteworthy topographic depression across the Appalachian 
tract is the lowland of central New York. It is remarkable for its con- 
tinuity from Lake Erie to the Hudson, its low gradients and elevation, 
its thoroughgoing transection of the upland in which it occurs, besides 
its swarms of drumlins and its narrow, deep, picturesque lakes and 
bordering glens. Among its exceptional features are to be noted also 
its dense population, numerous and busy railways, its canals, and its 
long and romantic historical development. In many of these respects 
it is a happy contrast to the adjacent provinces. The Adirondacks on 
the north are more gramd, but they are thinly peopled, have few rail- 
ways, and limited resources. On the south the uplands of the Appa- 
lachian Plateaus are also thinly populated. In recent years they have 
suffered a relapse into the ways of a back country and exhibit an increas- 
ing number of abandoned farms. ^ Between these two rugged uplands 
extends the relatively narrow central valley with its deep, fertile soil, 
pleasing countrysides, and prosperous homes. 

The geologic map of New York, Fig. 285, largely explains the central 
valley. The strata outcrop in westward- trending belts and the thick- 
ness and interrelations of the hard and soft members from place to 
place determine both the local topographic expression and the width of 
the central valley (Plate IV). The southern border of the lowland is the 
frayed northern border of the Appalachian Plateaus. Spurs from 10 to 
20 miles long, from 2 to 5 or more miles wide, and from 100 to 500 feet 
high extend north on the interfluves between the deep narrow valleys 
whose floors are occupied by lakes. The border is maintained definitely 
because of a capping layer of hard sandstone. The central lowland is 
developed upon the Salina and Hudson River shales and other soft 
formations. Formerly the strata extended farther north, overlapping 
and wrapping about the Adirondack old-land. When first uplifted above 
the sea the sediments formed a simple coastal plain. In time this plain 
was dissected, and since the soft formations weathered more rapidly, 

1 R. S. Tarr, Decline of Farming in Southern-Central New York, Bull. Am. Geog. Soc, vol. 
41, 1909, pp. 270-278. 

707 



7o8 



FOREST PHYSIOGRAPHY 



they were worn to a lowland, while the hard formations stood in relief. 
Similar features extend westward across Ontario and through northern 




LAKE 



Fig. 284. — Physiographic belts in central New York. Heavy dotted line is on the divide. Figures 
represent elevations above sea level. (Modified from Fairchild.) 

Michigan and eastern Wisconsin, as shown in Plate V. They represent 
an old coastal plain so eroded as to present both its structure and its 
relief in rudely parallel belts, hence an ancient belted coastal plain. 



LOWLAND OF CENTRAL NEW YORK 709 

The upper Susquehanna still pursues a consequent course; the Mohawk 
is a subsequent stream, while the normal courses of most of the streams 
farther west have been modified by glaciation. In such a description 
Lake Ontario and Georgian Bay lie upon the inner lowland, Lakes Erie 
and Michigan upon the outer lowland of the plain. In western New 
York the plain is a double depression separated by the Niagara escarp- 
ment which dies out east of Rochester. 

Many of the detailed topographic features of the depression of cen- 
tral New York, such as drumlins, lakes, glens, old abandoned channels, 
etc., depend chiefly upon glaciation. The ice advanced southward as 
far as northern Pennsylvania, overriding and somewhat modifying the 
divide between the Ontario and the Susquehanna-Allegheny drainage. 

Not everywhere in southern New York and northern Pennsylvania 
were moraines accumulated at the margin of the ice. In few localities 
does one find moraines developed on the uplands between valleys, 
though they are well developed in the valleys themselves. '^ As shown 
in Fig. 284 the valley heads draining north everywhere have well-defined 
morainic accumulations which were formed in front of local ice tongues 
that extended along each valley after the margin of the great con- 
tinental ice sheet had been melted from the inter-valley tracts. In 
addition there are three major features, more or less directly due to 
glaciation, whose character and mode of formation deserve attention. 
These are (i) the Finger Lakes, (2) the glacial-marginal drainage chan- 
nels, and (3) the drumlins of the central lowland. 

Finger Lakes 

The basins of the Finger Lakes were first generally explained as the 
result of ice erosion, a kind of glacial overdeepening, but with the action 
confined to a single glacial period. Later and more detailed studies 
have shown that the forces which produced these basins are complex in 
their nature and relations. Glacial erosion is indeed the most important 
element of the explanation, as the steepened sides of the basins, the 
hanging tributary valleys^ and the presence of lateral and terminal 
moraines at the valley heads testify. The last-named feature is clearly 
shown in Fig. 284, and proves that the valleys were highways of more 
active glacial motion. 

The most important facts pointing to complexity of origin relate to 
the hanging valleys tributary to the Finger Lakes. On the steepened 
slopes of the main valley sides a series of buried gorges has been found. 

• Williams, Tarr, and Kindle, Watkins Glen-Catatonk Folio U. S. Geol. Surv. No. 169, 
field ed., 1909, p. 124. 



7IO 



FOREST PHYSIOGRAPHY 



The gorges are occupied by drift deposits of the last (Wisconsin) ice inva- 
sion, which indicates that they were formed before that invasion.^ 

From the known facts it is concluded that before the glacial period 
there was a system of mature drainage with main valleys along the axes 
of Cayuga and Seneca lakes and with tributaries entering them at 
grade. With the overspreading of the region by glacial ice there was 
begun a process of exceptional deepening in the main valleys because they 
served as lines of most rapid glacial flow. At the end of the first ice 




UD 



EZ] B ^ 



[3 



MB 



ORDOVICIAN SILURIAN' DEVONIAN MISSISSIPPIAN 

Fig. 285. — Map of portion of New York, i, Ordovician; 2-5, Silurian; 6-13, Devonian; 14, Mississipian. 

invasion the valleys had been broadened and deepened, the amount of 
the deepening being about 500 feet. Lakes may have formed in these 
overdeepened valleys after the ice had been melted away. At any rate 
the discordance of level between tributary and master valleys was pro- 
nounced and the tributaries began to cut down their valleys to the level 
of the main valleys, making gorges of notable breadth and depth before 
the second glacial invasion filled them with drift, reexcavated and 
deepened the main valleys, increased the discordance between tributaries 
and master streams, and so altered the topography in detail that the 
postglacial streams do not flow everywhere in the interglacial courses. 
Wherever a postglacial stream enters one of these buried gorges with its 
easily eroded drift in contrast to the hard rocks of the rest of the valley 

1 R. S. Tarr, Watkins Glen and Other Gorges of the Finger Lake Region of Central New 
York, Pop. Sci. Mo., vol. 48, 1906, pp. 387-397. 



LOWLAND OF CENTRAL NEW YORK 711 

there the valley broadens suddenly; where the stream leaves the buried 
valley the valley contracts. It is these features, together with the 
irregular as well as regular jointing of the bedded rock — shales and 
sandstones — that give to the gorges so much of their surprising varia- 
tion from place to place and to the beautiful waterfalls and cascades of 
the many glens their wild, picturesque quality. 

The lower portions of the valleys of the tributaries to each of the 
Finger Lake basins are for the most part more or less completely drift- 
filled gorges, so that the rock floor is in many cases far below the drift 
floor of the valley, a condition brought about not by overdeepening of 
the main trough but by the clogging of the tributary valley with drift. 
There are, however, perfect examples of hanging valleys with rock floors in 
the Cayuga and Seneca troughs and in the Tioughnioga and Cay uta valleys.^ 

The abrupt descents of the valley slopes in the Finger Lake region is 
illustrated by the change at the 900- foot contour just west of Watkins 
in the Cayuga trough. The slope from the 900-foot contour to the 
valley bottom, which has an elevation of 477 feet, takes place in a dis- 
tance of a little over a half mile, while west of the 900-foot contour the 
valley side rises only 700 feet in a distance of 5 miles. ^ 

Abandoned Channels 

Among forms indirectly due to glacial action an important part is 
taken by the features relating to marginal drainage of the ice, such as 
have been described for the Great Lake region and will now be noted 
for the central New York region. In central New York the northward 
slope of the margin of the Appalachian Plateaus furnished unusual 
conditions for the impounding of glacial waters in front of the retreat- 
ing ice cap, when that front had receded northward so as to lie beyond 
the divide between the Lake Ontario and the Susquehanna drainage. 

The earliest accumulations of ice dammed the waters at the heads of 
the great valleys on the south. Upon the gradual retreat of the ice 
lower outlets were offered past the ice margin and across the ridges or 
plateau spurs between the lakes, so that high valley lakes drained into 
lower valley lakes; as the ice front receded still farther the lakes were 
successively lowered and shifted northward and rivers formed in the 
inter- valley or spur tracts. In central New York all the glacial waters 
escaped westward to the glacial lake in the Erie basin and ultimately 
to the Mississippi River, from a point west of Batavia; and the same is 

» R. S. Tarr, Watkins Glen and Other Gorges of the Finger Lake Region of Central New 
York, Pop. Sci. Mo., vol. 48, 1906, p. 233. 

2 R. S. Tarr, Drainage Features of Central New York, Bull. Geol. Soc. Am., vol. 16, igos, 
pp. 320-242. 



712 



FOREST PHYSIOGRAPHY 



GLACIAL LAKE 
SUCCESSION IN 
NE1VT01JK STATE ///, 

LAKE NEAVBERRY 




Fig. 286. — Note overflow southward into the Susquehanna. Elevation over 1000 feet. 




Fig. 287. — Overflow at this stage was westward to the Mississippi instead of southward to the Susque- 
hanna. Elevations from 1000 feet on east to goo feet on west. 



LOWLAND OF CENTRAL NEW YORK 



713 



true of all the waters held in the Genesee region under about 1200 feet, 
as well as in several other lake regions. But all the drainage under 
900 feet at a later period was eastward past Syracuse to the Mohawk 
Valley. In the general region of the Finger Lakes between Batavia 
and Syracuse at least 13 separate valleys sloped to the north and these 
He from Oatka Valley on the west to the Onondaga at the east, and 
include such important valleys as the Genesee, Canandaigua, and 
Cayuga. The higher and more local glacial waters in these valleys 




. GLACIAL LAKE 
SUCCESSION IN 
NE>VyOKK STATE 

LAKE IROQUOIS 
L44 Scale of Miles 



Fig. 288. — Overflow eastward to the Mohawk. Elevation under 360 feet. A number of intermediate 
stages are omitted from this series. The three stages shown here are of chief importance. (After 
Fairchild, Bull. N. Y. State Mus.) 

escaped southward, but at later stages the water of the broad area 
collected here mainly into two large lakes, one of which occupied the 
large low central valleys of Seneca, Cayuga, and Keuka, with an outlet 
to the Susquehanna, and another in the Genesee Valley region which 
escaped by a different route to the Susquehanna, Allegheny, and Mis- 
sissippi. In a later stage of development and before the beginning of 
the extensive spur channeling so prominent in central New York, these 
two bodies of water were united into one extensive lake overflowing 
westward into the Mississippi drainage above 900 feet and eastward to 
the Hudson below that level. 

A study of the channels which drained the valleys of the separate 
lake waters through a single outlet shows that they lie in series falling 



714 



FOREST PHYSIOGRAPHY 




LOWLAND OF CENTRAL NEW YORK 



715 



northward on the theory of a receding barrier, though not as controlled 
by a steady continuous single recession of the ice front but by an 
oscillation of the ice front and a certain amount of seesawing between 
Batavia and Syracuse.^ 

Typical features of the channel series may be seen at Spread Rock 
and Jamesville and on the meridians of Mumford and Rush, etc. They 
were carved directly in front of the ice, and in such a position that the 




Fig. 290. — Gulf channel, looking southeast (downstream) near mouth of channel. Four miles north of 
Skaneateles, New York. The depth of the gorge is 100 to 150 feet, the width from an eighth to a 
quarter of a mile. The walls are of shale. The gorge ends in a huge fan delta. (Gilbert.) 

streams that occupied them must in many cases have laved the ice 
front, in which case only the southern banks are now in existence, since 
the northern banks were formed by the glacier ice. In some instances, 
as in the case of the Fairport-Lyons channel, the channel that was ini- 
tiated on the ice front remained effective long after the ice had retreated 
from the region. 

The most compact and remarkable set of cross-ridge channels is north 
of the parallel of Jamesville; the lowest is the finest glacial lake outlet 

» H. L. Fairchild, Glacial Waters in Central New York, Bull. New York State Mus. No. 127, 
pp. 7-10. 



7l6 FOREST PHYSIOGRAPHY 

channel in the state. It is 2 J miles long, 800 to 1000 feet wide at the 
bottom, and 125 to 155 feet deep in rock. The channel sides are com- 
posed of nearly vertical limestone. The highest channel of the James- 
ville group is associated with a cataract, a semicircular amphitheater 
about 100 feet in diameter, with steep limestone walls 160 feet high; 
Jamesville Lake, 60 feet deep and 400 to 500 feet across, occupies the 
plunge basin at the foot of the cataract. Below the cataract is a gorge 
cut in limestone, and above it the limestone is worn and terraced in a 
manner characteristic of rapids. 

NIAGARA FALLS 

Niagara Falls came into existence during the retreatal stages of the 
continental ice cap of the Wisconsin epoch. For a time ' the glacial 
marginal waters were confluent over both the Erie and Ontario basins 
and extended northward as far as the ice barrier, but with the lower- 
ing of the water level the escarpment of Lockport limestone gradually- 
emerged. This escarpment held up the Erie waters to its upper level, 
while the level of the Ontario water was controlled by the relations of 
the ice and the topography at the northern escarpment in lower country. 
Thus the waters of Lake Erie came to cascade over the cliff of Niagara 
limestone and drop into the water of the Ontario basin. As the Ontario 
waters receded the river cascaded over the scarp and formed a gorge 
which by upstream retreat had gradually been brought into its present 
position and character. The first spilling of the Erie waters over the 
escarpment took place at at least two points of overflow, one at Lockport 
and one at Lewiston ; but by the more rapid development of the Lewis- 
ton channel the Lockport channel was abandoned.^ 

Drumlin Types and Belts 
Among topographic forms due to glaciation drumlins are scarcely 
less important in areal extent and importance to soils than terminal 
moraines. They deserve a word of detailed description not only for 
this reason but also because of the remarkable development of drumlins 
in certain areas in New York, Wisconsin, etc., where their slopes con- 
stitute the most important elements of the relief. That the forms of 
drumlins are of glacial origin is evident from the location of drumlins 
only within glaciated areas; that their material is of glacial origin is 
shown also by their composition, which is for the most part compact 
till or ground moraine, and their position in the zone in which the trans- 
porting power of the ice was incompetent to carry along all the material 

1 H. L. Fairchild, Glacial Waters in Central New Yorli, Bull. New York State Mus. No. 127, 
p. 30. 



LOWLAND OF CENTRAL NEW YORK 



717 



within it. In form they vary from mounds to long slender ridges, their 
most general form being a smooth oval; in size they vary from massive 
conspicuous hills from 100 to 200 feet high to indefinite swells of drift sur- 
face. A less common type of drumlin than the one described above has 
been known as the drumloid or, as has been lately proposed, roc drumlin.^ 
The term is employed to designate ice-made rock masses whose form is 
so closely allied to that of the drumlin as to deserve correlation with it. 




Fig. 291. ■ 



■ Roc drumlins or druraloids. The drumlin-shaped forms in the upper part of map are developed 
on shale (Salina). (Baldwinsville quadrangle, U. S. Geol. Surv.) 



They are distinct from the more common type of drumlin in that they 
are due to erosion, while the ordinary drumlin is a product of upbuild- 
ing and of shaping. Roc drumlins occur in much smaller numbers than 
ordinary drumlins, but are sometimes found in the same general field, 
as in central New York and northern Wisconsin and Michigan. The 
last-named occurrence has been described by Russell.^ 

Three general regions of great drumlin development have been iden- 
tified in the United States: (a) the New England area, including southern 
New Hampshire, where about 700 drumlins have been mapped, Massa- 
chusetts with about 1800, and Connecticut with an unnumbered amount; 
(b) the Michigan area, which includes eastern Wisconsin and adjacent 

» H. L. Fairchild, Drumlins of Central- Western New York, Bull. New York State Mus. 
No. Ill, 1907, p. 393. 

» I. C. Russell, Rapt. Mich. State Geologist, 1906. 



7i8 



FOREST PHYSIOGRAPHY 



PART OF CHERRY CREEK QUADRANGLE 



PART OF OVID QUADRANGLE 




PART OF CLYDE QUADRANGLE 



PART OF CANANDAIGUA QUADRANGLE 




Fig. 292. — ^ Topographic types, central New York, i, rock" forms, non-glacial; 2, till-covered slopes, 
expressionless; 3, drumlins;'4, moraine. (Fairchild.) 



LOWLAND OF CENTRAL NEW YORK 719 

portions of Michigan, where the estimated number is 5000; and (c) the 
drumHn area of central New York. The last-named is a belt about 35 
miles wide bordering the southern side of Lake Ontario and about 140 
miles long, from the Niagara River to Syracuse; this area probably in- 
cludes not less than 10,000 drumlin crests; 15 drumlins to the square 
mile is common, though the average is about 3 to the square mile. 

On the south the drumlin area of central New York reaches up the 
north-facing slope of the Allegheny plateau, where it fades off into smooth 
drift or is lost in the bolder relief of the rock hills. The most abrupt 
ending of the drumlin topography is along the crests of ancient drainage 
levels, as between Victory and Geneva, New York. The most massive 
development is on the low ground north of Finger Lakes and south of 
Lake Ontario, chiefly under 500 feet altitude. The greatest development 
lies over the greatest thickness of the soft Salina shales, where the drift 
is most clayey and adhesive. Those on the southern border of the 
drumlin belt are attenuated, while those toward the north and under 
the deeper ice are broad. The greatest steepness and greatest regularity 
of form seem to occur in the middle of the drumlin belt. 

The drumlins have been but little modified in postglacial time by 
ordinary stream erosion, but in the zone of wave erosion on the southern 
shore of Lake Ontario, as at Sodus Bay, the drumlins have been exten- 
sively cut or entirely removed, and similar shore cutting was accomplished, 
though on a smaller scale, during the existence of temporary glacial- 
marginal lakes that occurred at a higher level than Lake Ontario during 
the later stages of the glacial period. The general relations of the drumlin 
area of central New York to the surrounding topographic features are 
shown in Fig. 292. The various categories of form are indicated in the 
following table: 

" I. Domes or mammillary hills and low broad mounds. 

2. Broad oval drumlins. 

3. Oval drumlins of high relief. 

4. Long oval drumlins, commonly bolder on the north or struck end; the dolphinback or 

whaleback hills. 

5. Short ridge drumlins. 

6. Long ridge drumlins. This includes two extreme varieties of form: (a) the long broad 

ridges or rolls or gentle swells which are not generally recognized as belonging in the 
drumlin class, and commonly fail of representation on the contoured maps; (b) the 
small, close-set, parallel ridges which lie as minor moldings between the larger and 
conspicuous ridge drumlins, or those which form the attenuated edge of a drumlin belt. 

7. Abrupt struck slopes. 

8. Low or gentle struck slopes. 

9. Sharp-crested hills with steep, or even concave, side slopes. Many occasional or pecul- 

iar forms and characters might be noted, but they are not regarded as genetically 
important." 1 
I H. L. Fairchild, Drumlins of Central-Western New York, Bull. New York State Mus. 
No. Ill, 1907, pp. 422-423. 



720 FOREST PHYSIOGRAPHY 

In regard to the relation of drumlins to moraines it may be said that 
the moraines are weak where the drift was left in drumlin form and 
strong where the drift was not drumlinized.^ The drumlins are be- 
lieved to be shaped by the sliding movement of the lowest ice, a move- 
ment that was produced by thrust on the marginal ice, caused by the 
pressure rearward applied in such a manner that the margin of the ice 
was pushed bodily forward. It is believed that this condition of ice move- 
ment is fundamental to drumlin formation.- In this manner the drum- 
lins were constructed by a plastering-on process on the obstructions, a 
process favored by the plastic and adhesive drift. As masses of drift 
the drumlins were produced by the accretion of drift, but their peculiar 
form is due to erosion. The whole process has been aptly compared 
to clay modeling, a process of plastering on and rubbing away.^ 

1 H. L. Fairchild, Drumlias of Central- Western New York, Bull. New York State Mus. 
No. Ill, 1907, p. 425 et al. 

2 Idem, p. 430. 

3 Idem, p. 432. 



APPENDIX A 



Soil Class; Soil Type; Soil Series i 

SOIL CLASS 

Because soils are made up of particles of different sizes, they may be grouped according to 
texture, that is, according to the relative proportions of the particles of different sizes which 
they contain. This grouping is known as the "soil class." By means of mechanical analyses 
the particles less than 2 millimeters in diameter are separated into 7 grades and the various per- 
centage relationships of the different grades determine the class of soil — sand, sandy loam, loam, 
clay, etc., as in the table below. In addition to the fine earth, of which a mechanical analysis 
is made, many soils contain larger particles, which if of small size are called "gravel," and if 
of larger size are called "stones," so that in the soil classification it is possible to have a gravelly 
sand, loam, or clay, and likewise stony members of the various classes. 

In outlining soil boundaries, it is necessary to (i) make preliminary borings in sufficient 
number to show the location of a considerable body of soil material of uniform character, 
(2) record the general description of one or more borings, (3) select a color to represent this 
description and color in so much of the map as undoubtedly corresponds with the description, 
(4) work away from this identified area until soil materials are found which manifestly do not 
fit the former description, (5) select a second color for this new set of soil characteristics and 
color in on the map only where the new material undoubtedly occurs, (6) work in between the 
areas of the two classes thus established until a zone or line is found where all material on one 
side becomes increasingly characteristic of the one class and on the other side of the other class, 
(7) draw a line on the map to represent this line or to represent the center of the zone of gra- 
dation of soil characteristics. This line will constitute a soil boundary. Usually the distinctions 
between adjacent soil classes are sharp and clear in a moderately broken country and grade into 
each other in a flat country, although there are many exceptions to this rule. In a glaciated 
region the mixing action of the ice may thoroughly confuse the rock waste, so that the most 
minute examination is required for the separation of many soil classes distributed almost at 
haphazard. Sometimes this is true to such an extent that a new designation is required, such 
as the geologic term "till," although this should be avoided if possible. Drainage differences 
and attendant differences in the content of organic matter, depth of soil, etc., may constitute 
a basis of distinction. Postglacial wash is sometimes responsible for considerable differentiation 
of material, which may be made the basis of distinctions between soil classes. When minor 
differences of texture, structure, organic-matter content, or succession of materials occur in the 
soil sections representing single areas of 10 acres or more, such variations may be described 
in the report as phases. 

The soils of different classes grade into each other and therefore the line of separation be- 
tween the different classes is necessarily an arbitrary one. The particles also may be very 
irregularly distributed between the different grades, so that it is not possible to make a rigid 
classification according to the mechanical analyses. The following table is the result of an 
examination of thousands of soil samples from all over the United States by the U. S. Bureau 
of Soils and may be accepted as a standard for the classification and description of the soils 
of a given area, large or small. Uniformity and close adherence to the standard are the chief 
considerations which it is desired to secure. The table therefore constitutes a codification and 

' Based on the Soil Survey Field Book, 1906- 
721 



722 



APPENDIX 



arrangement of facts reported up to this time to the Soil Survey. It has been found convenient 
to number the different grades into which the soil is separated by mechanical analysis. The 
name of the grade to which these numbers refer is given in the table. Care should be taken 
in interpreting the table not to confuse these grades for either the soil class or the soil type. 



SCHEME OF SOIL CLASSIFICATION BASED UPON THE MECHANICAL 
COMPOSITION OF SOILS. 



Class. 


1. 

Fine 
gravel. 

2-1 

tnm. 


2. 

Coarse 
sand. 

i-.s 

mm. 


3. 

Medium 
sand. 

• 5-25 
mm. 


4. 

Fine 
sand. 
.2S-.I 
mm. 


5. 

Very fine 
sand, 
.i-.os 
mm. 


6. 

Silt. 

■os-.oos 

mm. 


7. 

Clay. 
.005-0 
mm. 




More than 25 per 
cent of I +2. 








o-iS 


O-IO 


Coarse sand. 


Less than 20 per cent 
of 6+7. 


More than 50 per cent of 

1+2+3. 




Less than 25 per ! 
cent of I +2. 






0-15 1 o-io 


Medium sand. 


Less than 20 per cent 
of 6+7. 


More than 20 per cent of 

1+2+3. 




Less than 20 per cent of 

1+2+3. 




0-15 1 o-io 


Fine sand. 


Less than 20 per cent 
of 6+7. 




More than 20 per cent of 

1+2+3. 






IO-3S 1 S-iS 


Sandy loam. 


More than 20 per 
cent and less than 
50 per cent of 6 +7. 




Less than 20- per cent of 

1+2+3. 






IO-3S 1 5-15 


Fine sandy 
loam. 


More than 20 per 
cent and less than 
50 per cent of 6+7. 












- 


1 15-25 


Loam. 


Less 
than 55 
per cent 

of 6. 






More than 50 per 
cent of 6+7. 


Silt loam. 












More 
than 55 
per cent 

of 6. 


Less 
than 25 
per cent 

of 7. 














25-SS 1 25-35 


Clay loam. 


More than 60 per 
cent of 6+7. 


Sandy clay. 












Less 
than 25 
per cent 

of 6. 


More 
than 20 
per cent 

of 7. 




Less than 60 per 
cent of 6+7. 


Silt clay. 












More 
than 55 
per cent 

of 6. 


25-35 

per cent 

of 7. 


Clay. 














More 
than 35 
per cent 

of 7. 




More than 60 per 
cent of 6 +7. 



APPENDIX 723 

SOIL TYPE 

In mapping a small area the soil class is the matter of chief and possibly even of ultimate 
interest. The determination of the class tells about all the facts of texture that a forester 
requires. When, on the other hand, large areas are under consideration it may be necessary 
to distinguish soil types. A soil type is conceived to embrace all soil material in any region 
which is marked to corresponding depths by identity or close similarity in texture, structure, 
■organic-matter content, and color, and by similarity of origin and of topography. A type 
comprises all soil material which may properly be included in one general description cover- 
ing these points. In the humid regions description covers the material to an average depth 
of 3 feet; in the arid regions to a depth of 6 feet. In the determination of a type of soil 
there are many factors to be considered in addition to texture, such as the structure, which 
deals with the arrangement of the particles and their chemical composition, the organic- 
matter content, origin, color, depth, drainage, topography, native vegetation, and natural 
productiveness. The value of the type idea lies in the possibility of distinguishing between 
two soils of, let us say, practically identical texture, whose chemical composition, depth, 
bumus content and drainage conditions, etc., are markedly unlike. Both may be, for example, 
sandy loams, but the one may possess other characteristics than textural which make it in- 
fertile, while the other may possess a high degree of fertility. 

son, SERIES 

In working in a very large territory such as the whole United States it has even been neces- 
sary to recognize still larger groups or soil series. It has been found that in many regions the 
members of a given set of soil types are so evidently related through source of material, method 
of formation, topographic position, and coloration, that the different types constitute merely 
a gradation in the texture of an otherwise uniform material. Different types that are thus 
related constitute a series. A complete soil series consists of material similar in many other 
characteristics but grading in texture from stones and gravel on the one hand through sands 
and loams to a heavy clay on the other. 

In arranging the soils in series the same factors should be considered that are used in sepa- 
rating soils of the same class into different types. For example, the Marshall silt loam and 
the Miami silt loam have been separated because of the difference in the amount and con- 
dition of the organic matter in the surface soil and the essential differences in coloration. The 
former is dark brown to black, while the latter is light brown to almost white. This relation, 
has been found to exist between soils of other classes in the glacial regions, and has been used 
as a basis for separating the glacial soils into the Marshall and Miami series. 

On account of the very different processes of their formation, residual and recent alluvial 
soils should not be included in the same series. Soils may, however, be very similar in origin 
and texture but occupy such entirely different topographic positions that their relation to crops 
is entirely changed, and this fact should be recognized by the use of another serial name. An 
example of this is found in the separation of the soils of the Piedmont Plateau and the Appa- 
lachian Mountains into the Cecil and Porters series. 

The color of the soil is one of its most noticeable physical features, and is often a factor in 
separating the soils into different series. The soils of the Orangeburg series, for examole, have 
been formed in a manner very similar to the Norfolk series, but are distinguished from the 
latter by the red color of the subsoil and by associated differences in agricultural value. Soil 
series may grade into each other in a manner similar to the intergradation of the types 
within the series. Thus the Marshall series may grade into the Miami series and the Norfolk 
series into the Orangeburg or Portsmouth series. 

Unclassified Materials; Special Designations 
There are certain conditions of soil, or in many areas even local absences of true soil, which 
do not readily fall into any general classification. They may be due to excessive erosion, to 
overflow, to insufEcient drainage, or to wind action, or the soils may be infertile on account 
■of their texture or their present topographic position. Areas of this kind are as follows: 



724 APPENDIX 



ROCK OUTCROP 



Areas consisting of exposed rock or fresh accumulations of stone, entirely unfit for cul- 
tivation. The most extensive areas of this type of surface are found in the strongly glaciated 
portions of northeastern Canada. The type is also common in mountain regions-undergoing 
vigorous dissection and in wind-swept arid regions, etc. 



ROUGH STONY LAND 



Areas so stony and broken as to be nonarable, although permitting timber growth and pas- 
turage. They frequently consist of steep mountain ridges, bluffs, or narrow strips extendng 
through definite soil types. These areas differ from rock outcrop by supporting vegetation 
of economic value, and from the stony loams in being nonarable. 



The surface consists of a light-brown or reddish-brown sandy loam or loam underlain by 
soft saccharoidal gypsum at a depth of from a few inches to 5 feet. Gypsum is often present 
at the surface. The type occupies level bench land. It is derived from disintegration of 
gypsum deposits and possesses remarkable power of transmitting seepage waters by capil- 
larity and gravitational flow. Where the irrigation water possesses a high salt content this is 
not a desirable land for agricultural purposes. It often contains large quantities of alkali. 



Vegetable matter consisting of roots and fibers, moss, etc., in various stages of decompo- 
sition, occurring as turf or bog, usually in low situations, always more or less saturated with 
water, and representing an advanced stage of swamp with drainage partially established. 



This type consists of black, more or less thoroughly decomposed, vegetable mold from i to 
3 feet or more in depth and occupying low, damp situations, with little or no natural drainage. 
Muck may be considered an advanced stage of peat brought about by the more complete de- 
composition of the vegetable fiber and the addition of mineral matter through deposition from 
water or from aeolian sources, resulting in a finer texture and a closer structure. When drained, 
muck is very productive and is adapted to a large variety of agricultural crops. Extensive 
areas of it occur in the glaciated Middle West, where it grades into peat or swamp on the one 
hand and into conventional soil classes on the other. 

M.ADELAND 

Areas are occasionally encountered where filling has taken place over considerable tracts. 
The arrangement of the materials and even the materials themselves may be artificial and not 
in harmony with any soil classification. In many instances such areas are extensive and 
should be represented by a color on the map. 

DUNESAND 

Dunesand consists of loose, incoherent sand forming hillocks, rounded hills, or ridges of 
various heights. Dunes are found along the shores of lakes, rivers, or oceans, and in desert 
areas. They are usually of little value in their natural condition on account of their irregular 
surface, the loose, open nature of the material, and its low water-holding capacity. Dunes 
are frequently unstable and drift from place to place. The control of these sands by the use 
of windbreaks and binding grasses is frequently necessary, as at Cape Cod and on the coast 
of CaHfomia, for the protection of adjoining agricultural lands. In certain regions they have 
been improved for agricultural purposes or employed as catchment areas in city water sup- 
plies or planted to pine forest for the protection of agricultural land and for revenue. 



APPENDIX 725 



This term is used to describe ridges and uneven areas of sand not in motion, either on 
account of partial consolidation or because the sands are fixed by a natural growth of grasses 
such as the Sand Hills tract of western Nebraska. Such areas sometimes occur in the vicinity 
of old shore lines of lakes and seas; again they may be related to river action, as where flood 
plains are alternately flooded and drained and river sands exposed to the winds. 

RIVERWASH 

Sand, gravel, and bowlders, generally in long narrow bodies, but occasionally spread out 
in fan-shaped areas. These areas occupy river bottoms or flood channels, and occur where 
the streams are intermittent or liable to torrential overflow. They are of such recent origin 
as not to be covered by vegetation and are subject to modification during the next season of 
high water. The flood plains of the Missouri and the Platte supply examples. 



Low-lying, flat, usually poorly drained land, such as may occur in any soil type. Fre- 
quently used for grass, pasturage, or forestry, and can be changed to arable land if cleared 
and drained. The present character of meadowland is due to lack of drainage, and the term 
represents a condition rather than a classification according to texture. The soils vary fre- 
quently in texture, even within small areas and on account of occasional overflow the charac- 
ter of the soil at any one point is subject to change. Wherever it is possible to separate such 
areas into distinct soil types the term meadow should not be used. 



This term is used to designate low, wet, treeless areas, usually covered by standing water 
and supporting a growth of coarse grasses and rushes. Marsh areas occur around the borders 
of fresh-water lakes and the lower courses of streams. They can seldom be drained without 
diking and pumping. When this is done the soil is usually productive. 



Areas too wet for any crop and covered with standing water for much or all of the time. 
Variations in texture and in organic-matter content may occur. Swamp frequently occupies 
areas which are inaccessible, so that detailed mapping is impossible. The native vegetal 
growth consists of water-loving grasses, shrubs, and trees. Many areas of swamp are capable 
of drainage, and when this is properly accomplished they not infrequently constitute lands of 
high agricultural value. Drainage may be employed also to improve the soil by aerating the 
organic matter and permitting humification, or it may make possible the introduction of new 
forest types. The salt-water swamps of the Coastal Plain, the swamps of the glaciated region 
of northern United States and Canada, and the river swamps are the three chief occurrences. 
Wherever small areas of swamp occur within a definite soil type and the texture of the soil is 
known to be the same as that of the surrounding type, they should be mapped with the type 
and the swampy condition shown by symbol. 



APPENDIX B 



The various factors of importance in a study of soils are summarized in the accompanying 
outline. It is intended to present only a suggestive outline. A categorical adherence to this 
outline is very undesirable, since a condition or a brief list of conditions may be of such pre- 
dominating influence in determining the value of a soil as quite to obscure other conditions. 
Not all the suggestions are applicable to a given small area; as many as possible should be 
identified and others not in the table should be found. The relative value of the soil qualities 
should be strongly brought out in every soil survey and greatest attention given to those of 
most prominence. Under special conditions this principle may properly be carried so far as to 
ignore even the standard mechanical classification of soils. 

Outline for a Soil Survey in Forest Physiography 

Location and Boundaries of Area — 

Present condition as to settlement. 
Chief towns. 

Transportation facilities. 
Markets, etc. 

Topography and Drainage — 

Geologic structure and rock types. 

Topographic forms and stage of physiographic development. 

Brief description of the regional surface drainage in relation to form and structure; 
stream gradients and sizes, characteristics of valley sides and floors in relation to run-off, 
seepage, floods, etc. 

Climate — 

Direction and strength of winds. 

Relation to plant distribution. 

Rainfall: amount, frequency, and distribution in the year. 

Disposal as controlled by geologic and physiographic conditions; the regional run-off, 
absorption, evaporation. 

Daily and yearly temperature variations, extremes and means; relief controls of tem- 
perature and rainfall; proximity to the sea, latitude, etc. The growing season, tempera- 
tures necessary for germination and growth, degree to which climatic conditions meet 
the needs of forest types. 

Soils — 

(i) A general study of the soils of the area, showing their broad relation to the geologic 
formations and to each other, to drainage, erosion, and other agencies, their classifica- 
tion and distribution. (2) A detailed and full description of the classes of soil and sub- 
soil, noting texture, structure, color, depth, and ease of cultivation; follow this with a 
statement as to the location of various soils in the area, topographic and drainage fea- 
tures, origin and process of formation, peculiar mineral or chemical features — as alkali, its 
chemical composition and vertical distribution, and approximate area; native vegeta- 
tion, its value in determining soil classes and its responses to them, etc. Unclassified 
materials that require special designation: rock outcrop, talus, marsh, dunesand, etc. 

726 



APPENDIX 727 

Underground water conditions. 

Depth of water table. 

Fluctuations of level. 

Occurrence of springs and seepage lines. 

Forms and effects of subirrigation. 

Charactei" of ground water and reclamation possibilities. 
Soil temperature as related to: 

Air temperature. 

Slope exposure. 

Underground water conditions. 
Soil fertility; cultural methods and conditions that have effected or will effect improve- 
ments. 

The soil humus, forest litter, drainage effects upon, maintenance by shading, by pro- 
tection from the wind. 



m 



APPENDIX C 



ANALYSES OF FIVE COMMON ROCK TYPES IN THEIR FRESH AND IN THEIR 
DECOMPOSED CONDITION 

(From Merrill's Rocks, Rock-weather ing, and Soils.) 



Constituents 



Til 



Ignition 

Silica (Si02) 

Titanium (Ti02) 

Alumina (AI2O3) 

Iron protoxide (FeO) . . 
Iron sesquioxide (Fe203! 

Lime (CaO) 

Magnesia (MgO) 

Soda (Na20) 

Potasii (K2O) 

Phosphoric acid (P2O5) . 



1.22% 
69.33 
not det. 
14-33 

3 -60 



3-21 

2.44 
2. 70 
2.67 
o. 10 



99.60% 



3.27% 
66.82 
not det. 
15.62 

1.69 

1.88 

3-13 

2.76 

2.58 

2.04 
not det. 



99-79% 



4-70% 
65.69 

0-31 
15-23 



4-39 
2.63 
2.64 



0.06 



99-77% 



1 (I) fresh gray granite, (II) brown but still moderately firm and intact rock, and (III) the 
residual sand. 



ANALYSES OF FRESH AND OF DECOMPOSED GNEISS, ALBEMARLE COUNTY, VIRGINIA 



Constituents 



Silica (Si02) J li; JJ^'cQ^ 

Alumina (AI2O3) 

Iron sesquioxide (Fe203) . 

Lime (CaO) 

Magnesia (MgO) ....... 

Potash (K2O) 

Soda (Na20) 

Phosphoric acid (p205) . . 
Ignition 



Fresh 
Gneiss 



Bulk 
Analysis 



60.69% 

16.89 
9.06 
4.44 
1.06 
4.25 
2.82 
0.25 
0.62 



Decom- 
posed 
Gneiss 



Bulk 
Analysis 



45-31% 

26.55 

12.18 

Trace 

0.40 



0.47 
13-75 

99.98% 



I Gain. 



728 



Calculated Amounts Saved and 
Lost 



III 



Loss 



31.90% 

0.00 
1.30 
4-44 
0.80 
3-55 
2.68 
0.00 1 
0.00 I 

44-67% 



IV 



Percentage 

of Each 
Constituent 

Saved 



47-55% 

100.00 

85-65 

0.00 

25-30 

16.48 

4-97 

100.00 

100.00 



V 



Percentage 

of Each 

Constituent 

Lost 



52-45% 
0.00 

14-35 
100.00 

74-70 

83-52 

95-03 
0.00 1 
o.ooi 




APPENDIX 



729 



ANALYSES OF FRESH AND OF DECOMPOSED DIORITE FROM ALBEMARLE COUNT\', 

VIRGINIA 



Constituents 



Silica (SiOo) 

Alumina (AI2OS) 

Iron sesquioxide (Fe203) 1 

Lime (CaO) 

Magnesia (MgO) 

Potash (K2O) 

Soda (Na.,0) 

Phosphoric acid (P2O5) . . . 
Ignition 



Fresh 



46.75% 
17.61 
16.79 
9.46 

5-12 

o.SS 
2.56 
0.25 
0.92 

100.01% 



Decom- 
posed 



42.44% 
25.51 
19. 20 

0.37 

o. 21 

0.49 

0.56 

o. 29 
10.92 



90-99% 



Calculated 
Loss for En- 
tire Rock. 



17.43% loss 
0.00 
3-53 
9. 20 
4.97 
o. 21 
2. 17 
0.00 



37.51% loss 



Percentage 
of Each 

Constituent 
Saved 



62.69% 

100.00 

78.97 

2. 70 

2.83 

61.25 

15-13 

80.11 

100.00 



Percentage 

of Each 

Constituent 

Lost 



37-31% 

0.00 
21.03 
97-30 
97.17 
38.75 
84.87 
19.87 

0.00 



ANALYSES OF FRESH AND OF DECOMPOSED ARGILLITE, HARFORD COUNTY. 

MARYLAND 



Constituents 



Silica (Si02) 

Alumina (AI2O3) 

Iron oxide (FeO and Fe203) 

Lime (CaO) 

Magnesia (MgO) 

Potash (K.>0) 

Soda (Na20) 

Ignition (C and H2O) 



Fresh Ar- 
gillite 



44-15%) 

30.84 

14.87 

0.48 

o. 27 

4.36 

0.51 

4.49 



99-97%o 



Residual 
Clay 



24-17% 
39-90 
17.61 
None 

0.25 

I. 24 

0.23 
16.62 



100.02% 



Percentage 

of Loss for 

Entire 

Rocli 



25-34% 



1.23 
0.48 
0.08 
3-39 
0.33 
0.00 



40.83% 



Percentage 

of Each 

Constituent 

Saved 



42.43% 

100.00 

91. 22 

0.00 

71.84 

22.04 

0.36 

287.37 



Percentage 

of Each 

Constituent 

Lost 



57.57% 

0.00 

8.78 
100.00 
28.16 
77-95 
99.64 
None 



ANALYSES OF FRESH LIMESTONE AND ITS RESIDUAL CLAY 



Constituents 



Silica (Si02) 

Alumina (AI2O3) 

Ferric iron (Fe203) 

Manganic oxide (MnO) 

Lime (CaO) 

Magnesia (MgO) 

Potash (K..0) 

Soda (Na20) 

Water (H2O) 

Carbonic acid (CO2) . . . 
Phosphoric acid (P2O5) . 



Fresh 
Limestone 



4.13% 

4.19 

2-35 

4-33 
44-79 

0.30 

0.35 

o. 16 

2. 26 
34-10 

3-04 



100.00% 



Residual 
Clay 



33.69% 
30.30 

1.99 
14.98 

3.91 

o. 26 

0.96 

o.6r 
10.76 

0.00 

2.54 



Percentage 
of Loss for 

Entire 

Rocli 



0.00% 

0.35 

2.13 

2.49 
44.32 

6.2s 

0.23 

0.085 

0.95 
34.10 

2.73 



100.00% 97.635%) 



Percentage 

of Each 

Constituent 

Saved 



100.00% 
88.65 
10.44 
42.41 
1.07 
10.62 
33.63 
46.74 
58.37 
0.00 
10. 24 



Percentage 

of Each 

Constituent 

Lost 



0.00% 
11-35 
89.56 
57.59 
98.93 
89.38 
66.37 
53.26 
41.63 
100.00 
89.76 



APPENDIX D 



TEE GEOLOGIC TIME TABLED 





Old classification 






New classification 








Cambrian 

Ordovician or 
Silurian 


Lower 


f Georgia 
■{ Acadic 
(^Ozarkic or Cambric 

fCanadic 
-{ Ordovicic _ 
l.Cincinnatic 


"> 


i-Paleozoic 


Paleozoic . 




.- 


Siluric 
Devonic 




Siluric 
Devonic 














Mississippian or 
Sub-Carboniferous 


( Mississippic 
( Tennesseic 






■Neopaleozoic 








Pennsylvanic- 
.Permic 




Pennsylvania 
Permic 




. 








fTriassic 




Triassic-Jurassic 


1 


Mesozoic . 




J Jurassic 
I, Cretaceous 

'Eocene 
Oligocene 




( Comanchic 
( Cretacic 

1 Eogenic 


- 


>Mesozoic 

1 


Tertiary or 


Cenozoic. 


' ' Miocene 








l-Neozoic 








Pliocene 
^_PIeistocene 




1 Neogenic 




J 





1 The new classification is suggested by Charles Schuchert, Paleogeography of North Amer- 
ica, Bull. Geol. Soc. Am., vol. 20, 1910. 



730 




IGNEOUS ROOKS 



f 



INDEX 



Abajo Mountains, 277. 

Abbe, C, Jr., General Report on Physiog- 
raphy of Maryland, 500, 516, 517, 623. 

Absaroka Mountains, situation in 
Rocky Mountains, 329; topography of 
East and West Boulder plateau in. 
Fig. 105, p. 333; topography of, 335; 
glacial features of, 335 ; topographic map 
of, Fig. 106, p. 336; forests of, 337. 

Adirondack Mountains, dry timber line 
of, 232; of northeastern New York, 
555; altitudes of, 578; geologic struc- 
ture of, 578; topography and drainage 
of, 579; plateau-like western portion of, 
Fig. 234, p. 580; roundness of mountain 
forms in, 580; fault topography of, 
581; mountain profiles in, 581; rec- 
tangular pattern of relief and drainage 
lines in fault-block mountains of. Fig. 
235, P- 582; fault valleys of, 583 
glacial effects on, 583; drift in, 583 
local glaciation of, 583; climate of, 584 
forests of, 584; relation to Newer 
Appalachians province, 666. 

Advance Lowland, 528. 

Aftonian Interglacial Interval, 466, 
467. 

Agassiz, a.. The Elevated Reefs of Florida, 
548, 550- 

Agassiz, Louis, Former Existence of 
Local Glaciers in White Mountains, 648. 

Air in Soils, amount of air space, ^^■, 
aeration of meadows in Holland, 34. 

Alabama-Mississippi Section of 
Coastal Plain, soils of, 521; black 
prairies of, 522; trunk streams in, 522; 
outer edge of, 522; savannas of, 523; 
abandoning of the old fields of in Ala- 
bama, 524. 

Algonkian and Iroquois Beaches, iso- 
basic map of, Fig. 188, p. 484. 

Alkali Salts, amounts and composition 
of. Fig. II, p. 99. 

Alkali Soils, composition of, 97; two 
types of, 99. 

Allegheny Front, 666, 670, 672, 685. 

Allegheny Mountains, portions of, 
685. 

Allegheny Plateau, run-off, 5; rela- 
tion to Appalachian Plateaus, 685; 



soils of, 692; distribution of morainal 
deposits and direction of ice movement 
in western New York, Fig. 279, p. 693; 
vegetation of, 693; mature dissection 
of in West Virginia, Fig. 280, p. 694. 

Alps, Pyrenees, Vosges, rocks of in 
relation to bacteria, 17. 

Aluminum, as soil element, 67. 

Amaragosa Valley, 228. 

Ancha Range, 246. 

Anderson, F. M., Physiographic Fea- 
tures of the Klamath Mountains, 142. 

Anderson Mesa, 283. 

Andree, Hand atlas, 128. 

Animas Mountains, tree growth of, 
249, 250. 

i\NTELOPE AND Pereis Valleys, alkali 
soil of, 100. 

Antillean Flora, in Florida, 126. 

Apatite, and phosphoric acid, 72. 

Appalachian Mountains, soil of, 23; 
height of, 603. 

Appalachian Plateaus, members of, 
588; relation to great Appalachian 
Valley, 666; relation to Allegheny 
Front, 670; northern district of, 685- 
694; northern border of, 686; north- 
south section across northern edge 
of. Fig. 275, p. 686; eastern margin of, 
686; topography of, 687; topographic 
levels in, 688; warped surface of early 
Tertiary peneplain of central Appa- 
lachians, Fig. 276, p. 688; section 
illustrating terraces of Ohio Valley, 
Fig. 277, p. 689; effects of glaciation of, 
689; Pocono Plateau in, 690; present 
and pre-Pleistocene courses of Monon- 
gahela and Youghiogheny rivers. Fig. 
278, p. 690; Catskill Mountains in, 
691; central district of, 694; mag- 
nificent forests of central district of, 
695; southern district of, 695; Cum- 
berland Plateau in, 695; Walden 
Ridge in, 695; Lookout Mountains in, 
695; the Highland Rim in, 695; phys- 
iographic development of southern 
district of, 697; " barrens " of, 698; 
limestone soils of, 698; local lowlands 
of, 700. 

Appalachian Ridges, as distinctive 
features in the topography, 671; ex- 



731 



732 



INDEX 



planation of, 672; topographic forms 
of, 675. 

Appalachian System, general features 
of, 585; former forest cover in, 585; 
drainage map. Fig. 235a, p. 587; sub- 
divisions of, 588; geologic features of, 
589; structural relations of the parts 
of. Fig. 236, p. 589; categories of form 
in, 590; physiographic development of, 
590; unity of expression and origin of 
forms in, 591; cretaceous peneplain of, 
591; axes of deformation of in southern 
Appalachians, Fig. 237, p. 593; suc- 
cession of erosion cycles in, 594; phys- 
iographic map of southern Appalach- 
ians in, Fig. 238, p. 595; names of 
peneplain in, 596; relation of topog- 
raphy to rock types of, 596; curve 
illustrating relation of topographic 
relief to lithologic composition in, 
Fig. 239, p. 598; glacial effects in, 599; 
probable pre-glacial drainage of W. 
Penn., Fig. 240, p. 599; drainage 
changes due to glaciation of, 600; 
topographic effects of glaciation of, 
601; maximum stage of Lake Passaic 
in. Fig. 241, p. 601; amount of till de- 
posited in, 601. 

Appalachian Valleys, limestone soils 
of, 698. 

Aquarius Plateau, location in high 
plateaus, 262; topography of, 263; 
vegetation of, 263; compared with 
Kaiparowits Plateau, 264; high precip- 
itation of, 288. 

Arbuckle Mountains, rehef of, 456; 
mixed hardwoods in typical relation 
to topography, Fig. 172, p. 457; tree 
growth in, 457. 

Argillite, analyses of fresh, and of 
decomposed, 729. 

Arid Soil, salts of, 95; lime of, 95; floccu- 
lated condition of, 95 ; nitrogen content 
of soil humus, 96; clay in, 96; phos- 
phoric acid in, 97; potash in, 97. 

Arid West, stream characteristics of, 
210. 

Arizona Highlands, topography and 
drainage of, 246; mountain structures 
of, 246; creeks of, 246; annual pre- 
cipitation of, 247; soils of, 247; vegeta- 
tion of, 247; waste-bordered moun- 
tains of, Fig. 68, p. 248; character of 
tree growth of, 249; Clifton district in, 
250; Bradshaw Mountains in, 251; 
Santa Catalina Mountains in, 253; 
eastern border features of, 253; rain- 
fall of, 254; rings of growth of trees 
of, 254; and Grand Canyon district, 
268; and San Francisco Plateau, 272; 



topographic profile in relation to rain- 
fall, Fig. 81, p. 286. 

Arizona, topographic profile S. W. to 
N. E., Fig. 81, p. 286. 

Arkansas River, headwaters of, 409. 

Arkansas Valley, structure of, 455. 

Ark-i-linik, Hudson Bay tributary, 
forests of, 41. 

Arnold and Anderson, Geology and 
Oil Resources of the Coalinga District, 
44, 184. 

Arnold, Ralph, Geological Reconnais- 
sance of Coast of Olympic Peninsula, 
144. 

Aroostook County, Me., glacial till 
in, 641. 

Arrows Peak, 331. 

Artillery Lake, and transcontinental 
spruce forest, 570. 

Asheville, rock areas near, 607; local 
peneplain at, 609; basin, 610, Fig. 245, 
p. 611. 

Ashley, H. E., Colloid Matter of Clay 
and its Measurement, 36. 

Asnebumskit Mountain, 637. 

Asotin, gorge at, 196. 

Atlantic and Gulf Coastal Plain, 
general features and boundaries, 498; 
special features of, 498; border rela- 
tions, 498; fall line, 499; relation to 
continental shelf, 499; materials of, 
500; subdivisions of, 501; Cape Cod- 
Long Island section of, 502-514; New 
Jersey-Maryland section of, 514-518; 
Virginia-North Carolina section of, 518, 
519; South Carolina-Georgia section 
of, 519, 520; Alabama-Mississippi sec- 
tion of, 520-524; a " break " in, 524; 
a " gulf " in, 524; Mississippi Valley 
section of, 524-528; black prairies of, 
522, 525; Louisiana-Texas section of, 
529-539; soils of, 539; tree growth of, 
540-542. 

Atlantic Forest, trees of, distribution 
of, 125. 

Atwood, W. W., Glaciation of Uinta and 
Wasatch Mountains, 268, 345, 347. 

Aubrey Cliffs, 270. 

Aughey, S., U. S. Geol. aiui Geog. Surv. 
of Col. and Adj. Terr., 428. 

Augusta, location in fall hne, 499. 

Austin, location in fall line, 499. 

Avalon, sand dunes of, 504. 

Awapa Plateau, location in High Pla- 
teaus, 262; topography of, 263; vegeta- 
tion of, 263. 

Ayres and Ashe, The Southern Appa- 
lachian Forests, 612. 

Ayres, H. B., Washington Forest Reserve, 
165. 



INDEX 



733 



Baboquivari Range, 245. 

Bacteria, in soil formation, 17; action 
of in relation to nitrogen, 86; size of, 
86; functions and value of, 86; fed upon 
by protozoa, 88; nitrogen changes in 
soil produced by, Fig. 9, p. 89; and 
direct fixation of nitrogen from soil 
air, 90; in symbiosis with alga;, 90; in 
symbiosis with legumes, 90; anaerobic 
or denitrifying, 90; in root nodules, 92. 

Badlands of the Black Hills Re- 
gion, factors controlling the develop- 
ment of, 415; scarcity of deep-rooted 
vegetation in, 415; details of, Fig. 149, 
p. 415; rainfall of, 416; topographic 
complexity of, 416; important topo- 
graphic element of, 416; stream flow 
in, 416. 

Balcones Fault Zone, section of, Fig. 
.162, p. 435. 

Bald Eagle Valley, 677. 

Bald Mountain, 321. 

Baldwin Lake, 136. 

Bally Choop Mountains, 141. 

Balsam Mountains, spruce forests of, 
614. 

Barlow, A. E., Report on Geology and 
Naktral Resources of Area between the 
Nipissing and Teniiskaming, 559. 

Barrell, J., Geology of MarysviUe Mining 
District, Montana, 319. 

Barren Grounds, relation to transcon- 
tinental spruce forest, 570. 

Barren Lands, elevation of, 560. 

Barrows and Bolster, The Surface 
Water Supply of the U. S., 644. 

Bartlett, W. H., Experiments on the 
Expansion and Contraction of Building 
Stones, 15. 

Basin Ranges, longitudinal profiles of. 
Fig. 55, p. 219; structure of, 220; geo- 
logic history of, 221; fault-block 
mountains of, 221; variation in topo- 
graphic development of, 222; of central 
portion, 222; evidences of fault-block 
origin of, 223; mountain border and 
internal structure of, 223; continuity 
of range crest of, 224; evidences of 
progressive and recent faulting, 225; 
broken waste slopes of, 225; stream 
profiles and recent faulting in, 226; 
terminal facets of mountain spurs of, 
227; springs and fault lines of, 228; 
Death Valley region of, 228; and Ari- 
zona Highlands, 246. 

Bateman, Can. Geol. Siirv., 567. 

Battenkill Valley, 682. 

Bay of Fundy, 626. 

Bear Butte, 445. 

Bear Lake, and San Bernardino Range, 
136; water of, 212. 



Bear Paw Mountains, 412. 

Bear River Mountains, 198, 202. 

Bear River, volume of, 217. 

Beartooth and Neighboring Pla- 
teaus, canyons of, 332; topography of 
East and West Boulder Plateau, Fig. 
105, p. 2>ii\ glacial features of, 334. 

Bear Valley, and the adjacent country,. 
Fig. 27, p. 137. 

Beech Creek, 671. 

Belknap Range, trend of, 645. 

Bell, R. M., Proofs of Rising of the Land 
around Hudson Bay, 563; Geographical 
Distribution of Forest Trees in Canada, 

571- 

Belt Mountains, 302. 

Berlin Valley, 683. 

Berkshire Hills, usage of the name, 
681; fertility of, 683. 

Berkshire Valley, 683. 

Berry Mountain, 673. 

Berthelot ANT) Andre, Comptcs Ren- 
dus Academie de Paris, 88. 

Betts and SiCTH, Utilisation of Cali- 
fornia Eucalypts, 145. 

Bigbug Mesa, and lava flows, 251. 

Bigelow, F. H., Studies of Diurnal 
Periods in Lower Strata of Atmosphere, 

Bighorn, height of, 157. 

Bighorn Mountains, section across 
highest part of, Fig. 113, p. 349; struc- 
ture and topography of, 349; east side 
of limestone front ridge of. Fig. 114, 
p. 350; subordinate topographic fea- 
tures of, 351; high mountains in, 351; 
glacial forms of, 351; wall at head of 
cirque. Fig. 115, p. 352; former glacier 
systems of, Fig. 116, p. 353; surviving 
glaciers of, 353; lakes of, 354; forests 
on, 354; cretaceous deposits on, 419. 

Big Mountain, 673. 

Birch, red, temperature requirements of, 
55; and aspen in relation to soil erosion, 
78. 

BiscAGNE Bay, 543. 

Bitterroot Mountains, and Snake 
River Valley, 202; and Blue Mountains, 
207; in Northern Rockies, 298; profile 
across. Fig. 102, p. 321; map of part of. 
Fig. 103, p. 325; eastern border features 
of, 326; main divide of, 326; soils of, 
327; forests of, 327. 

Bitterroot Valley, 321. 

Black Butte, 445. 

Black Dome Mountain, 691. 

Black Hills, ideal east-west section 
across. Fig. 164, p. 440; structure of, 
441; western slope of, Fig. 165, p. 441; 
soils of, 442; forest of, 443; outlying 
domes of, 444. 



734 



INDEX 



Black Log Valley, 677. 

Black Mesa, and lava flows, 251; and 
surface of San Francisco Plateau, 273; 
junipers on, 287. 

Black Mountains, direction of, 607. 

Black Prairie, section of. Fig. 162, p. 
435; topography of, 491. 

Black Range, 390. 

Block Island, former condition of, 502. 

Blue Grass Country, topographic fea- 
tures of, 701; structure of, 701; northern 
portion of Cincinnati arch. Fig. 282, 
p. 702; residual soils of, 702. 

Blue Hill, Me., section of. Fig. 261, 
p. 646. 

Blue Mountains, Oregon, place of 
study of relations of present and buried 
topography, 195; and plain of the 
Columbia, 202; situation, 207; topog- 
raphy of, 208; geologic features of, 
208; effects of lava flows, 208; precipi- 
tation of, 209; forests of, 209. 

Blue Ridge, mountain forms west of, 
608; falls of the Linnville at, 610; 
elevation of, 612; coves of, 620; plateau 
and escarpment of. Fig. 251, p. 620; 
highest portion of, 621; view of with 
Catoctin Mountain and Bull Run 
Mountain in Virginia, Fig. 252, p. 621; 
cross sections of the Catoctin Belt, 
Figs. 252a, 253, p. 622; relation to 
Newer Appalachians province, 666, 
670; mountain folds near, 672. 

Boise Ridge, 324. 

Boise River, 198. 

BoLSONS, definition of, 398; description 
of, 398. 

Bonneville, Lake, and Great Salt Lake, 
214; shore features of, 214. 

Book or Roan Plateau, 278. 

Boreal Province, characteristics of, 122. 

Boston Mountains, structure of, 452; 
dominating height of, 453. 

Boundaries, between the Sierra Nevada, 
Cascades, Coast Ranges, and the 
Klamath Mountains, Fig. 28, p. 141. 

BOUSSINGAULT AND LeVY, 9. 

Bowman, I., Northward Extension of 

Atlantic Preglacial Deposits, 502. 
Boyd Lake, relation to transcontinental 

spruce forest, 570. 
Bradshaw Mountains, relief of, 251; 

view of, Fig. 69, p. 252; precipitation 

and vegetation, 253. 
Brand egee, T. S., Teton Forest Reserve, 

344- 
Branner, J. C, Ants as Geological 

Agents in the Tropics, 20; Geologic 

Work of Ants in Tropical America, 20; 

Science, 534. 



Branner, Newsom and Arnold, Santa 
Cruz Folio U. S. Geol. Surv., 132, 133, 
146. 

Bray, W. L., Timber of Edwards Plateau 
of Texas, 429, 436, 438, 439, 440; 
Forest Resources of Texas, 542. 

Brewer, W. H., On Suspension and 
Sedimentation of Clays, 103. 

Bridger Range, in S. W. Monta,na, 315; 
relation to Big Horn Mountains, 349. 

British Columbia, Interior Plateau of, 
159- 

Britton, W. E.J Vegetation of the North 
Haven Sand Plain, 662. 

Brown and Escombe, Static Diffusion 
of Gases and Liquids in Relation to 
Assimilation of Carbon and Trans- 
location in Plants, 54. 

Brown, R. M., Protection of Alluvial 
Basin of the Mississippi, 526. 

Bruckner, E., Kliniaschwankungen seit 
1 700, nehst Bemerkungen iiber die Klini- 
aschwankungen der Diluvialzeit, 255. 

BuENA Vista, lake, 184. 

Buffalo or Seven Mountains, 673. 

Buffalo Rock, 196. 

Bullfrog District, Nevada, plan of 
faults in. Fig. 56, p. 220; fault-block 
displacements in, 220. 

Bunker Hill Dike, San Bernardino, S. 
California, effect on ground water, 46. 

Burlington Escarpment, 454. 

Bushnell, D. I., Jr., Science, 534. 

Buzzard's Bay, nearness to Cape Cod 
Bay, 503. 

Caballos Mountains, and Trans-Pecos 

Mountains, 390; of fault-block type, 

391; western escarpment of. Fig. 137, 

P- 392- 
Cabinet Range, in Northern Rockies, 

298; topographic features of, 305; 

southern end, Idaho, Fig. 90, p. 305; 

glaciation of, 306. 
Cache la Poudre River, 330. 
C.A.IRO Lowland, 528. 
Calcasien River, character of, 529. 
Calcium, as soil element, 68. 
Calhoun, F. H. H., Montana Lake of 

Keewatin Ice Sheet, 414. 
California, Gulf of, 177. 
California, southern, climate of, 118; 

coast ranges of, 127; map of. Fig. 24, 

p. 129; coastal terraces. Fig. 25, p. 134; 

northern, coastal topography of, 134; 

northern and southern compared, 179; 

east- west differences of climate, 179; 

West Riverside district, Fig. 46, p. 

187; Fig. 47, p. 187. 
Calkins and McDonald, Geological 



INDEX 



735 



Reconnaissance in N. Idaho and N. W. 
Montana, 306. 

Calkins, F. C, Geology and Water Re- 
sources of a Portion of East-central 
Washington, 193, 201, 203, 206; Geo- 
logical Reconnaissance in N. Idaho and 
N. W. Montana, 298, 300, 304, 327. 

Callahan Divide, on Great Plains of 
Texas, summits of. Fig. 160, p. 433; 
outlying mesas of Edwards Plateau, 

434- 

Caloosahatchee River, 547, 549. 

Camas Prairie, 321. 

Camden, location in fall line, 499. 

Cameron and Bell, Mineral Constit- 
uents of the Soil Solution, 12, 19, 53, 63. 

Campbell, M. R., Basin Range Structure 
in Death Valley Region of S. E. Cal., 
228; Drainage Modifications and their 
Interpretation, 678; Geological Develop- 
ment of N. Pennsylvania and S. New 
York, 687; Richmond Folio U. S. Geol. 
Surv., 701, 702. 

Canadian Valley, 397. 

Canandaigua Valley, 713. 

Canyon Lands, 258. 

Cape Chidley, 563. 

Cape Cod, former condition of, 502; 
canal across, 503; rate of wear of, 503; 
foundation of, 503; surface material of, 
503; control of sand dunes on, 504; 
pitch-pine plantations on, 505. 

Cape Henlopen, sand dunes of, 504. 

Cape Henrietta Maria, 561. 

Cape Henry, sand dunes of, 504; reefs 
of, 518. 

Cape Lookout, reefs of, 518. 

Cape Malabar, 553. 

Cape Romano, 543. 

Capillary Action, nature of, 51. 

Capillary Water, about soil grains, 
Fig. 7, p. 51; limits of adequacy of, 53. 

Capitan Range, tree growth in, 402; 
timber belts. Fig. 145A, p. 403. 

Capps, S. R. Jr., Pleistocene Geology of 
Leadville Quadrangle, 368. 

Carbonation, 9. 

Carbon Dioxide, amount in soil air, 
9, II. 

Carbonic Acid, destructive action of 
water charged with, 11. 

Carlisle Prong, 631. 

Carman, J. E., Mississippi Valley be- 
tween Savanna and Davenport, 495, 526. 

Carobabi Range, 245. 

Carriso Mountains, 277. 

Carrisos Mountains, 275, 276. 

Carr, M. E., The Volusia Soils, 104. 

Carson Lake, relation to Lake Lahonton, 
214. 

Carson River, run-o£f, 216. 



Carson Valley, 171. 

Casa Diablo, Cal., 168. 

Cascade Mountains, continuity of, 149; 
earlier descriptions of, 149; volcanoes 
of, 150; origin of, 150; accordant ridge 
crests of. Fig. 31, p. 151; details of 
topography. Fig. 32, p. 152; uniformity 
of summit levels. Fig. ^2>j P- '^Si'-> ^59) 
Plateau of. Fig. 36, p. 159; and Colum- 
bia River, 160; and Lake Chelan, 161; 
soil, climate, and forests of, 162; and 
timber line, 163; and Pacific Coast 
downfold, 177; cause of dryness on 
Columbia Plateaus, 202; sage bush 
east of, 206; cold timber line, 207. 

Cascade Pass, 150. 

Castle Rock, 206. 

Castleton Valley, 682. 

Catawba River, power of, 612. 

Catawissa Mountain, 673. 

Cathedral Peak, height of, 157; figure 
showing glaciated summit of, Fig. 35, 

P- 157- 

Catskill Mountains, relation to Newer 
Appalachians province, 666; relation to 
Allegheny Front, 670; relation to Ap- 
palachian Plateaus, 685; peaks of, 691; 
structure of, 691; ranges of, 691; 
drainage of, 692. 

Cayuga Valley, 713. 

Cedar Mountains, trees of, 234. 

Central Basin of Tennessee, 704. 

Central Cascades, uplifted peneplain 
of, 154; accordant summits of, 154; 
elevations of, 154; lava flows on, 154; 
eastern slopes of, 155; timber-tree 
species, altitudinal range and develop- 
ment of, Fig. 39, p. 164. 

Central Peak, 331. 

Central Rockies, asymmetry of folds 
in, 329; contrasts to Appalachian 
ridges, 329; map of, Fig. 104, p. 330; 
extra-marginal ranges, 345. 

Cerro Roblero, 399. 

Chamberlin and Salisbury, Geology, 
17, 466, 488, 647; Driftlcss Area of the 
Upper Mississippi, 496. 

Chamberlin, R. T., The Appalachian 
Folds of Central Pennsylvania, 672. 

Champlain Substage, of glacial period, 
466. 

Champlain Valley, relation to great 
Appalachian Valley, 665. 

Chattahoochee River, power of, 612. 

Chelan, Lake, description of, 160, 161; 
valley of, 301. 

Chemical Composition, of various types 
of organic matter, 83; of ulmin and 
ulmic acid, 84; of humin and humic 
acid, 84; of crenic acid, 84; of apo- 
crenic acid, 84. 



736 



INDEX 



Chewancan River, 225. 

Cheyenne River, 414. 

China, loess deposits, 24. 

Chinlee River, 275. 

Chiricahua Range, 246. 

Chisos Mountains, 387, 393, 402. 

Choiskai Mountains, 275. 

Chronological Order of Geologic 
Periods, 730. 

Churchill River, 557, 570. 

Cimarron River, 397. 

Cirque Development, conditions of, 
314- 

Clapp, F. G., Clay of Probable Cretaceous 
Age at Boston, 502. 

Clarke Fork, 332. 

Clarke, F. W., Data 0} Geochemistry, 
35, 64, 84. 

Clay, described, 35; colloid, 36; classifi- 
cation, 37; insolubility of, 39; affinity 
of for soluble plant food, 39; in arid 
region soils, 96. 

Claypole, E. W., Pennsylvania Before 
and After the Elevation of the Appalach- 
ian Mountains, 672. 

Clearwater Mountains, and Snake 
River Valley, 202; and Blue Mountains, 
207; in northern Rockies, 298; profile 
across, Fig. 102, p. 321; even summit 
levels of, 322; border features of, 322. 

Cleland, H. F., Effects of Deforestation 
in New England, 6. 

Clements, F. E., Life History of Lodge- 
pole Burn Forests, 50, 386. 

Clermont Hill Ridge, 172. 

Cleveland, T., Jr., Forests as Gatherers 
of Nitrogen, 93. 

Climatic and Life Provinces of N. 
America, Plate I, p. 122. 

Climatic Regions, factors, iii; ele- 
ments, III. 

Cloudcroft, 401. 

Coachella Valley, Salton Sink region, 
240. 

CoALiNGA District, of California, plant 
distribution of , 44, 62. 

Coal Mountain, 673. 

Coastal Terraces, produced by wave 
erosion, California, Fig. 25, p. 134. 

Coast Ranges of California, extent, 
127; subdivisions, names, height, mar- 
gins, 128; character of the relief, 130; 
the Rift, 130; northern, physio- 
graphic character of, 133; southern, 
135- 

Coast Ranges of Oregon, rocks of, 142; 
and the. Cascades, 143", eastern front 
of, 144; western front of, 144; border- 
ing terraces of, 144; topographic profile 
in relation to rainfall. Fig. 38, p. 163. 



Coast Ranges, of U. S., 127; extent of, 
127; subdivisions of, 127; climate, soil, 
and forests of, 145; timber lines of, 148; 
trees of, 148; timber line in. Olympic 
Mountains, 163; and Pacific Coast 
downfold, 177; origin of, 180; streams 
of eastern slopes, 182; and Lake Tulare, 
184. 

Coast Temperatures, Atlantic and 
Pacific contrasted, 112. 

Cobb, Collier, Notes on Geology of 
Currituck Banks, 501. 

CoBOTA Range, 245. 

Coconino Plateau, 271. 

CocopA Mountains, 241. 

CcEUR D'Alene Mountains, and plain 
of the Columbia, 202; in northern 
Rockies, 298; views of. Fig. 88, p. 303, 
and Fig. 89, p. 303; uniformity of 
summit levels in, 304; physiographic 
development of, 304. 

CcEUR D'Alene Valley, 301. 

Cole, L. J., The St. Clair Delta, 481. 

Collins, W. H., Report on Portion of 
N. W. Ontario between Lake Nipigon 
and Sturgeon Lake, 564. 

CoLLU\'iAL Soils, 23. 

CoLOB Plateau, 260. 

Colorado Desert, 184. 

Colorado Plateaus, soil of, 23; and 
Arizona Highlands, 246; physiographic 
features of, 256; relief of, 257; degree 
of dissection of, 258; breadth of can- 
yons of, 258; special features of, 258; 
individual members of, 259; districts 
of, 260; " water pockets " of, 261; 
scenery of, 272; physiographic develop- 
ment of, 281; erosion cycles in, 281- 
285; late geologic history of, 282; 
Black Point Monocline, Fig. 79, p. 282; 
climatic features of, 286; vegetation of, 
287; topographic profile in relation to 
rainfall, Fig. 81, p. 286; grassy growth 
on, 288; influence of elevation upon 
vegetation in, 289; mountains of the 
plateau province, 290; volcanoes of, 
292, 293; Mt. Taylor, prominent vol- 
canic elevation of, 296; Mogollon Mesa, 
area of high relief in, 296. 

Colorado Range, and central Rockies, 
329; cross folds on eastern border of, 
Fig. 119, p. 358; structure of, 362; 
peaks in, 362; border features of, 365; 
topographic clevelopment of, 365; old 
mountainous upland of Georgetown 
district. Fig. 123, p. 366; detailed topog- 
raphy of, 367; glacial features of, 368; 
tree growth in, 369. 

Colorado Ridge, 278. 

Colorado River Basin, soil erosion on, 
13- 



INDEX 



737 



Colorado River, volume of, 210; silt of, 
238; map of part of, Fig. 65, p. 239; 
change in course of, 240; irrigation 
along, 240; annual overflow of, 240; 
permanent stream of Moki-Navajo 
coxmtry, 274. 

CoBORADO Valley, map of part cf, Fig. 

65, P- 239- 

Columbia, location in fall line, 499. 

Columbia Plains, dust soils of, 204. 

Columbia Plateaus, extent and origin, 
192; buried topography beneath basalt, 
194; drainage effects of the basalt 
floods, 196; deformations of the basalt 
cover, 198; coulees of, 200; stream 
terraces of, 201; climate of, 202; soils 
of, 203; grazing on, 203; vegetation of, 
206; profile across, Fig. 102, p. 321. 

Columbia River, course of, 155; and 
Cascade Mountains, 160; lavas, 192, 
193; and Grand Coulee, 200, 201; 
lakes of the plain of, 201; utilization 
of water of, 205; volume of, 210; sand 
dunes along, 505. 

Columbus, location in fall line, 499. 

CoLviLLE Mountains, 302. 

Comanches Mountains, 390. 

CoNDRA, G. E., Geography of Nebraska, 

425- 

Connecticut Valley Lowland, and 
associated trap ridges, 645; general 
features of, 653; geologic structure of, 
653; relation of to bordering uplands, 
Fig. 263, p. 654; geologic and physio- 
graphic history of, Figs. 264A, 264B, 
p. 655; Figs. 264C, 264D, p. 656; 
faults and associated overlaps in, 656; 
advancing and retreating order of trap 
ridges of, 657; displacement of trap 
ridges near north end of West Rock 
Ridge, Fig. 265, p. 657; offset with 
overlap in, 657; offset with gap, 657; 
cretaceous peneplain of, 658; super- 
posed course of the lower Connecticut 
in, 658; inferred cretaceous overlap on 
the southern shore of Connecticut, Fig. 
266, p. 658; Tertiary peneplain of, 659; 
forms due to second uplift and to 
glaciation of, 660; soils of, 660, 662; 
North Haven sand plain or " desert," 
Fig. 267, p. 661; vegetation of, 662. 

Connecticut Valley, wearing of shales 
and sandstones in, 638; glacial till in, 
641, 648. 

CoNNELL, coulees near, 200. 

Continental Shelf, changes in position 
of, 500. 

Cooks Canyon, 172. 

Cooper, W. F., Water-Supply Paper, 
U. S. Geol. Surv., 473. 

Coosa River, power of, 612. 



Coosa Valley, relation to Great Appa- 
lachian Valley, 665; direction of, 683. 
Coos Bay Region, 142. 
Coppermine River, 570. 
CoRAzoNES Mountains, 393. 

CORDILLERAN CENTER OF ICE ACCUMULA- 
TION, 465. 

Corpus Christi Pass, 529. 

CoTEAu DES Prairies, 410. 

Cottonwood Cliffs, 269. 

Coulee City, 201. 

Cowlitz Valley, 177, 178. 

Crazy Mountains, 411. 

Cree Lake, 556. 

Cristobal Range, 391. 

Cross and Howe, Silverton Folio Col. 
U. S. Geol. Surv., 375; Needle Moun- 
tains Folio U. S. Geol. Surv., 378. 

Cross and Spencer, La Plata Folio 
U. S. Geol. Surv., 376, 378. 

Cross, W., Wind Erosion in the Plateau 
Country, 17; Mon. U. S. Geol. Surv., 
367; Pikes Peak Folio U. S. Geol. Surv., 
368. 

Crowley's Ridge, 524, 528. 

Crow Peak, 445. 

Crystal Falls District in the Su- 
perior Highlands, topography of, 
574; glacial soil of, 575. 

Cuchillo Negro Range, 391. 

Culebra Mountains, 409. 

Cumberlant) Escarpment, relation to 
Newer Appalachians province, 666. 

Cumberland Plateau, soil of, 23; rela- 
tion to Allegheny Front, 670; resistance 
of border rock in, 685; surface of, 696, 
698; map showing summit of. Fig. 281, 
p. 699. 

Cumberland Valley, relation to G.eat 
Appalachian Valley, 665; breadth of, 
666. 

Currituck Banks, sand dunes of, 504. 

Curtis and Woodworth, Nantucket, a 
Morainal Island, 506. 

CusHMAN, A. S., The Colloid Theory of 
Plasticity, 37. 

Custer Peak, 445. 

Dale, T. W., Taconic Physiography, 682. 

Dalles, The, 155. 

Dall, W. H., Neocene of North America, 

545- 

Daly, R. A., Nomenclature of N. A 
Cordillera between 47th and 53d 
parallels, 300, 301, 302; Geology of 
Northeast Coast of Labrador, 563. 

Danforth Hills, 278. 

Dartmouth Range, trend of, 645. 

Darton and Salisbury, Cloud Peak- 
Fort McKinney Folio U. S. Geol. Surv., 
349> 351, 354, 406. 



738 



INDEX 



Darton, Blackwelder, and Sieben- 
THAL, Laramie- Sherman Folio U. S. 
Geol. Surv., 331. 
Darton, N. H., Senate Doeument No. 219, 
345; Geology of Bighorn Mountains, 349; 
Geology and Underground Water Re- 
sources, Central Great Plains, 408, 419, 
420; Camp Clarke Folio U. S. Geol. 
Surv., 427; Geology and Underground 
Water of S. Dakota, 442; Washington 
Folio U. S. Geol. Surv., 625. 

Davis, , 283. 

Davis and Wood, Geographic Develop- 
ment of Northern New Jersey, 679. 

Davis, C. A., Peat, 82. 

Davis Mountains, 387, 393, 402. 

Davis, W. M., Elementary Meteorology, 
9; The Geographical Cycle in an Arid, 
Climate, 17; Physical Geography, 25, 
222; Mountain Ranges of the Great 
Basin, 223, 225; Ciirrent Notes in 
Physiography, 224; Glacial Erosion in 
Sawatch Range, 372; The United States 
in Mill's International Geography, 411, 
589; The Outline of Cape Cod, 503; The 
Geologic Dates of Origin of Certain 
Topographic Forms on the Atlantic 
Slope of the United States, 590, 591, 
637; Stream Contest along the Blue 
Ridge, 610; River Terraces in New 
England, 643; Rivers and Valleys of 
Pennsylvania, 679. 

Dawson, G. M., Trans. Royal Soc. 
Canada, 159. 

Deep River, 567. 

Deerfield River, valley of, 639. 

Delaware River, valley development 
of, 669. 

Denudation, in North America, 3 ; glacial, 
3; period of the great, 282. 

Desert Vegetation, typical view of, 
Fig. 63, p. 232. 

Desplaines Valley, 485. 

Detah Valley, 228. 

Detrital-Sacr.a.mento Valley, of Ari- 
zona, 238. 

Devil's Tower, Fig. 166, p. 444; 445 

Diamond Mountain, 172. 

DiLLER, J. S., Preliminary Account of 
Exploration of the Potters Creek Cave, 
140; Redding Folio Cal. U. S. Geol. 
Surv., 140, 181; Rosehurg Folio U. S. 
Geol. Surv., 139, 144; Coos Bay Folio 
U. S. Geol. Surv., 143; A Geological 
Reconnaissance in N. W. Oregon, 143; 
Bull. U. S. Geol. Surv., No. 353, 166, 
167; 14th Ann. Rept. U. S. Geol. Surv., 
167; Tertiary Revolution in Topogra- 
phy of Pacific Coast, 168; Geology of 
Taylorsville Region, Cal., 172. 



DiORiTE, analyses of fresh and of decom- 
posed, 729. 

Dirty Devil River, 292. 

Diversity of Soil, causes, 22^ 

Dnieper above Kiev, surface and under- 
ground water in basin of, 52. 

Doe River, gorge of, 610. 

Dog Mountains, tree growth, 249. 

Dole and Stabler, Water-supply, 13. 

Dolores Canyon, Fig. 78, p. 281. 

Dolores Plateau, in Grand River 
district, 277; topography of, 280; 
vegetation of, 280. 

Dolores River, 374 

Dona Ana Hills, 399. 

DoNNER UND Blitzen River, forests 
and stream flow in basin of, 6. 

Dorset, 681. 

Dorsey and Bonsteel, Soil Survey in 
the Connecticut Valley, 663. 

Dorsey, C. W., Reclaniation of Alkali 
Soils, 100; Reclamation of Alkali Land 
in Salt Lake Valley, 100. 

Douglass, A. E., Weather Cycles in 
Growth of Big Trees, 254. 

DowLiNG, D. B., Cretaceotis Section in 
Moose Mountain District of Southern 
Alberta, 307. 

Dragoon Range, 246. 

Driftless Area of Prairie Plains, 
soil of, 494; topographic qualities of, 
494; of Wisconsin, Fig. 192, p. 495; 
diagrammatic section in. Fig. 193, p. 
496; explanation of, 496; Niagara es- 
carpment in, 560. 

Drumlixs, types of, 716; rocdrumlins or 
drumloids. Fig. 291, p. 717; regions 
where developed, 717; types of in 
central New York, 719. 

Dubawnt River, 570. 

Duck Mountains, 410. 

Dunesand, 724. 

Dutton, C. E., Mount Taylor and Zuni 
Plateau, 256, 274, 277, 287, 296; Ter- 
tiary History of Grand Canyon District 
and Geology of High Plateaus of Utah, 
260, 261, 263, 264, 265, 268, 269, 270, 
271, 272, 273, 287, 289; 6th Ann. Rept. 
U. S. Geol. Surv., 402. 

Eagle Creek Range, 206, 208. 

Eagle Rock, 238. 

Earlier Wisconsin Stage, of glacial 

period, 466, 468. 
Earth Temperatures, of Edinburgh, 

Scotland, 15. 
Earthworms, burrows of. Fig. 2, p. 18; 

as soil builders, 19. 
East and West Boulder Plateaus, 

332, 323- 



INDEX 



739 



Eastern Border of the Rockies, Fig. 
141, p. 395. 

Eastern Foothills, Southern Rockies, 
hogback topography of, 357; structure 
of, 358; vegetation of, 358; other 
types of foothill topography, 359. 

Eastern New Mexico, physiographic 
subdivisions of. Fig. 150, p. 417. 

East Humboldt Range, trees of, 235. 

East Spanish Peak, 360. 

Ebauch and Macfarlane, Comparative 
Analyses of Water from Great Salt Lake, 
213. 

Ebermayer, E., Lehre der Waldstren, 
9, 47, 78, 79, 80. 

Edwards Plateau, area of, 431; relief 
map of, Fig. 158, p. 431; structural 
conditions of, 432; borders of, 432; 
drainage of, 433; subdivisions of, 433; 
variety of vegetation of, 434; section 
of. Fig. 162, p. 435; physiographic de- 
velopment of, 436; soil cover of, 436; 
vegetation of, 436; escarpment timber 
of, Fig. 163, p. 437; hill and bluff forest 
of, 438; " oak shinneries " of, 438; 

■ spread of mesquite on, 439; interrela- 
tions of forests, water supply, tempera- 
ture and soils in, 440. 

Eld ridge, G. H., Geological Reconnais- 
sance Across Idaho, 322. 

Elizabethtown, Tenn., 610. 

Elkhorn Range, 208. 

Elk Mountains, topographj^ of, 381. 

Elk Ridge, 275. 

Ellensberg, 154. 

El Paso, mean annual precipitation at, 
401. 

Elutriator, in position for soil analysis, 
Fig. 12, p. 103. 

Emerson, B. K., Holyoke Folio U. S. 
Geol. Surv., 643. 

Emmons, Cross, and Eldridge, Geology 
of Denver Basin in Colorado, 361, 383. 

Emmons, S. F., Desert Region, 234; U. S. 
Geol. Expl. of 40th Parallel, 267, 339, 
340, 342, 349; Uinta Mountains, 345; 
Science, 347. 

Emmons, W. H., Reconnaissance of 
Mining Camps in Central Nevada, 220. 

Endlich, F. M., U. S. Geol. and Geog. 
Surv. of Terr., 332; U. S. Geol. and 
Geog. Surv. of Col. and Adj. Terr., 373, 
376, 3&3- 

Ennadai Lake, relation to transcon- 
tinental spruce forest, 570. 

Erosion Effects, on mountain masses, 
Figs. 96, 97, 98, p. 316. 

Escalante River, 292. 

Esopus Creek, 691. 

EsTES Park, 386. 



Extra-marginal Ranges, relation to 
central Rockies, 345. 

Fairbanks and Carey, Glaciation in the 
San Bernardino Range, California, 138. 

Fairbanks, H. W., San Luis Folio U. S. 
Geol. Surv., 132, 147. 

Fairchild, H. L., Drumlins of Western 
New York, 468; Glacial Waters in Cen- 
tral New York, 715, 716; Drumlins of 
Central-ivestern New York, 717, 719, 
720. 

Fall Line, elevation of, 499; topography 
of, 499; relation to continental shelf, 

499- 

Fault-block Mountains, diagrams of 
Bullfrog district, Nevada, 220; of 
Basin Ranges, 221; of Great Basin, 
diagram of, 223; of Oregon, 224. 

Feather River, and depth of canyon, 
170; Middle Fork of, 171; forks of, 171; 
level of channel, 182. 

Feilberg, p., Om Enge og vedvarende 
Grasmarker, 42. 

Fenneman, N. M., Geology of Boulder 
District, Colorado, 362, 365; Physiog- 
raphy of St. Louis Area, 463. 

Fernald, M. L., Soil Preferences of 
Certain Alpine and Suhalpine Plants, 
62. 

Fernow, B. E., Relation of Forest to 
Water Supplies in Forest Influences, 4, 

Finger Lakes, 709-711. 

Fisher's Peak and Raton Mesa, Fig. 
140, p. 394. 

Fish Lake Plateau, 262. 

Flaming Gorge, 346. 

Flathead Range, in northern Rockies, 
298. 

Flint Hills, origin of, 408. 

Flocculation, of soils, 29; relation of 
lime, humus, etc., to, 29; action of clay 
on, 30. 

Florida, Bay of, 543. 

Florida, Peninsula of, general geogra- 
phy of, 543; keys and swamps of, 543; 
principal lakes and coastal features of. 
Fig. 220, p. 544; geologic structure of, 
545; physiographic development of, 
545; topography and drainage of, 546; 
pine forests of, 546; dunes of, 546; 
rolling sand plains of, 547; flat lands of, 
547; the Everglades of, 547, 548; "pine 
islands and cj'press straits " in, 547; 
rock ridges of, 548; swamps of, 548; 
Fig. 221, p. 549; coastal swamps of, 
550; the " Ten Thousand Islands " of, 
550; not a coral reef, 550; drainage 
features of due to karsting, 550; irregu- 
larity of drainage features of, 551; 
coastal islands of, 551; sounds of, 552; 



740 



INDEX 



keys of, 552; vegetal covering of is- 
lands of, 552; soils of, 552; subtropical 
or antillean forms of vegetation of, 553. 

FoLLANSBEE AND Stewart, Surface 
Water Supply of U. S., 409, 410; 
Missouri River Basin, Water-supply 
Paper U. S. Geol. Siirv., 410. 

Forest Distribution, effects of slope 
exposure on. Fig. 99, p. 318; Fig. 100, 
p. 318. 

Forest Regions, of U. S., 123; Fig. 21, 
p. 124. 

Forests, and stream flow, 4; of Ark-i- 
linik, 41; amount of rainfall necessary, 
43; Karst of Austria, 47; appropriation 
of free nitrogen, 93; Canada, 123; 
Atlantic, 125; Pacific, 125; western, 
Fig. 29, p. 146; of Sierra Nevada, 172- 
176; distribution of dominant conifers 
in Canada and eastern U. S., Fig. 228, 

P- 571- 

Fort Defiance, 275. 

Fox, John Jr., HeU-fcr-Sartin, 695; 
Blue Grass and Rhododendron, 695; 
Trail of the Lonesome Pine, 695. 

Fra Cristobal Mountains, New Mex- 
ico, western face of. Fig. 134, p. 389. 

Franklin Range, Texas, structure of, 
393; topography of, 393; section across. 
Fig. 138 and Fig. 139, p. 393. 

Frazer Rivzr, and Interior Plateau, 160. 

Freeman and Bolster, Surface Water 
Supply of U. S., 240, 242. 

Freeman, Lamb, ant) Bolster, Surface 
Water Supply of U. S., 401, 409. 

French Broad Ri\'Er, gorge of, 610; 
power of, 612. 

Front Range, see Colorado Range. 

Frost, last killing, in autumn, average 
date of. Fig. 17, p. 116; first killing, in 
spring, average date of, Fig. 18, p. 116. 

Fuller and Clapp, Ditney Folio U. S. 
Geol. Surv., 463. 

Funeral Range, 228. 

Gale, H. S., Gold Fields of N. W. Colo- 
rado and N. E. Utah, 278. 

Gallatin Range, in S. W. Montana, 
315; topography of, 317; lake basins of, 

317- 
Gallup, 275, 276. 
Galton Range, in northern Rockies, 

298; and longitudinal trenches, 302. 
Gannett, Henry, 19th Ann. Rcpt. U.S. 

Geol. Surv., 163, 296, 328; [/. S. Geol. 

and Geog. Surv. of Col. and Adj. Terr., 

279, 280, 381. 
Geikie, Sir Archibald, Textbook of 

Geology, 84; Geological Sketches at 

Home and Abroad, 192. 
Genesee Valley, 713. 



Geologic Section, from Colorado River 
to Colorado Plateaus, Fig. 67, p. 247. 
Geologic Time Table, 730. 
Georgian Bay, 560, 709. 
Gibbs, George, Physical Geography of 

N. W. Boundary of U. S., 155. 
Gila Mountains, 245. 

Gilbert, G. K., Science, 168; Lake Bon- 
neville, 213, 214; Geology of Portions 
of New Mexico and Arizona, 246; U. S. 
Geol. Surv. West of looth Meridian, 254; 
Report of Geology of Henry Mountains, 
292; Certain Glacial and Postglacial 
Phenomena of Maumee Valley, 478; 
Sufficiency of Terrestrial Rotation for the 
Deflection of Streams, 508. 

Glacial Detritus, of the Great Lake 
region, 24. 

Glaciation of Prairie Plains, centers 
of, 465; periods of, 466; topographic, 
drainage, and soil effects of, 469; four 
drift sheets of Wisconsin, Fig. 177, p. 
470; distribution of glacial moraines, 
Fig. 178, p. 471 ; glacial map of northern 
Illinois, Fig. 179, p. 472; drift cover {». 
Michigan, 473 ; Wisconsin icelobes about 
Driftless Area, Fig. 180, p. 473; ter- 
nal moraines in eastern North Da- 
kota, 473; relations of drift sheets of 
Iowa and northern Illinois, Fig. 181, p. 
473; southern limit of Pleistocene ice 
sheet and distribution of moraines of the 
Dakota glacial lake. Fig. 182, p. 474; 
drainage modifications, 474; effect on 
outlines of lake basins, 476; proglacial 
lakes, 477; and soils, 486; occurrence 
of loess deposits, 488. 

Glenn, L. C, Denudation and Erosion 
in the Southern Appalachian Region, 
615. 

Globe, Arizona, 254. 

Gneiss, analyses of fresh, and of de- 
composed, 728. 

Golden Gate, explanation of, 130. 

Goldthwait, J. W., Abandoned Shore 
Lines of Eastern Wisco7isin, 478. 

Goose Creek Mountains, 198, 202. 

Goose Lake Valley, 225. 

Goshen Hole, 421. 

Gould, C. N., Geology and Water Re- 
sources of the Panhandle, Texas, 419, 
424; Geology and Water Resources of 
Eastern Portion of Panhandle of Texas, 
422, 423; Geology and Water Resources 
of Oklahoma, 459, 464. 

Graciosa, back basalt sand on, 59. 

Grafton, L. C, Reconnaissance of some 
Gold and Tin Deposits of Southern 
Appalachians, 625. 

Grains, number of in a gram of soil, 27, 



INDEX 



741 



Grand Canyon District, members of, 
268; structure and topography, sections 
showing. Fig. 75, p. 268; and San 
Francisco Plateau, 272. 

Grand Canyon, mouth of, 254; relation 
to Kaibab Plateau, 271; cross profile of, 
Fig. 80, p. 285; relation to Marble 
Canyon, 285; divisions of, 285. 

Grand Coulee, interest of, 200; lakes 
of, 201. 

Grand EAU, — , Method for Determination 
of Humus, 83; Ann. Sci. Agr., 86. 

Grant) Hogback, 278. 

Grant5 Mesa, 277. 

Grand Prairie, and Edwards Plateau, 
434; topography of, 492. 

Grand River, 278. 

Grand River District, topography of, 
276; special border features of, 278; 
vegetation of, 290. 

Grand Wash Cliffs, and Colorado 
Plateaus, 256; and Grand Canyon dis- 
trict, 267; and Shiwits Plateau, 269; 
and San Francisco Plateau, 272. 

Grand Wash Valley, 269. 

Grant and Burchard, Lancaster-Min- 
eral Point Folio U. S. Geol. Surv., 463, 
494. 

Grant, U. S., Lancaster Mineral Point 
Folio U. S. Geol. Surv., 560. 

Graves, H. S., The Forest and the Nation, 
American Forestry, .7; Black Hills 
Forest Reserve, 443. 

Great Appalachian Valley, relation 
to Appalachian system, 588; elevation 
of, 612; composite character of, 665; 
western limit of, 666. 

Great Barrington, 681. 

Great Basin, arid region characteristics, 
hydrographic features, 210; salt lakes 
of, 210; drainage basins of, Fig. 53, 
p. 211; earlier climate of, 214; post- 
quaternary faults of, Fig. 54, p. 215; 
rivers of, 216; precipitation of, 216; 
special topographic features of, 217; 
topographic development of, 218; 
ranges of, 218; diagram of fault-block 
mountains of. Fig. 58, p. 223; soils of, 
229; forests and timber lines of, 230; 
vacant public land in. Fig. 61, p. 230; 
desert vegetation in southern part, 
Fig. 63, p. 232; characteristic trees of, 
233; most valuable trees of, 233; and 
Grand Canyon district, 268. 

Great Falls Lake, 413. 

Great Lake District, drainage history 
of southern part, Fig. 185, pp. 479, 
480; Superior ice lake, and glacial mar- 
ginal Lake Duluth, Fig. 186, p. 482; 
tilting of, 483; degree of stability of, 



483; map of extinct Lake Agassiz and 
other glacial lakes. Fig. 189, p. 484. 

Great Lakes, 560. 

Great Plains, rainfall of, 121; topog- 
raphy and structure of, 405; regional 
slope of, 405; geologic map of Texas 
regions. Fig. 146, p. 406; topographic 
and structural sections across, Hg. 147, 
p. 407; escarpments of, 408; stream 
types of, 409; regional illustrations, 
410-425; sand-hill country of, 425; 
total area of sand hills of, 425; im- 
portance of lakes of, 425; vegetation of, 
426; vegetation of the Texas regions, 
Fig. 157, p. 426; soil erosion of, 426; 
timber of, 427; tree planting in, 427; 
possibility of an earlier timber cover 
on, 427; condition governing treeless- 
ness of, 428; fineness of soil of, 428; 
prairie and forest fires of, 428; over- 
pasturing of, 429; prolonged droughts 
of, 429; cause of treelessness, 429; 
possibilities of reforestation of, 430. 

Great Plains Streams, spring floods 
of, 409. 

Great Sage Plains, 202. 

Great Salt Lake Basin, alkali soil of, 
100. 

Great Salt Lake, tons of salt in, 212; 
depth of, 212; changes in area of, 212; 
rate of evaporation of, 213; diversion 
of water of, for irrigation, 213. 

Great Sandy Desert, 203. 

Great Slave Lake, 570. 

Great Smoky Mountains, compared to 
Green Mountains, 588; direction of, 607; 
heights of, 608; spruce forests of, 614; 
relation to Newer Appalachians prov- 
ince, 666. 

Great Terrace of the Columbia, 201. 

Great Valley of California, and 
Pacific Coast downfold, 177; climatic 
features of, 179; rainfall of, 179; snow- 
fall of, 179; general geographic and 
geologic features of, 180; subdivisions 
of, 181; base-leveled plain on northern 
border of. Fig. 43, p. 182; forest growths, 
190. 

Green Bay, situation of on ancient 
coastal plain, 560. 

Greenhorn Ridge, 208. 

Green Mountain Plateau, origin of 
form of, 650. 

Green Mountains, rainfall of, 121; 
borders of, 588; effect of deforestation 
in, 619; exception to plateau feature 
of the province, 636; and bordering 
uplands, 645, 648; axis of, 649; northern 
section of, 649; middle section of, 649; 
southern section of, 650; transition up- 
land of, 651; glacial features of, 651; 



742 



INDEX 



mountain summits of, 651; eastern 
slopes of, 65 1 ; cultivation of upland of, 
652; abundant rainfall of, 652; soil 
conditions on lower valley slopes of, 
652; cover of, 652; relation to Newer 
Appalachians province, 666. 

Green River Basin, relation to Red 
Desert, 338; terrace and escarpment 
topography. Fig. 108, p. 340; topogra- 
phic types in, 341; gravel cover of, 342. 

Green River, relation to Uinta Moun- 
tains, 346; explanation of course of, 347. 

Gregory, H. E. (Gregory, Keller, and 
Bishop), Physical and Commercial 
Geography, 58; Field Notes, 274. 

Griswold, L. S., Notes on Geology of 
Southern Florida, 548. 

Grizzly Mountains, 172. 

Gros Ventre Mountains, situation in 
Rocky Mountains, 329; structural 
features of, 344. 

Ground Water, in relation to surface 
and bed rock. Fig. 5, p. 44; discussed, 
44; movement of, 45; effect on, of dike 
near San Bernardino, 46; changes in 
level of, 47; Slichter method of measure- 
ment of rate of flow, 48; lysimeter 
method of measurement of rate of flow, 
48; and root habits of trees, 49. 

Growler Mountains, 245. 

Gulf Coastal Plain, prominent topo- 
graphic features of. Fig. 212, p. 532; 
special features of, 533; mounds of, 533; 
cross section of, Fig. 213, p. 533. (See 
Atlantic aiul Gtdf Coastal Plain.) 

Gulf of Mexico, 410. 

Gulf of St. Lawrence, streams enter- 
ing, 561. 

GuYOT, Arnold, On the Physical Struc- 
ture and Hypsometry of the Catskill 
Mountain Region, 692. 

Gypsum, 724. 

Gypsum Hills, of Kansas and Nebraska, 



Hadley Lake, 643. 

Hager, a. D., Physical Geography and 

Scenery, Geology of Vermont, 649. 
Hagne, Arnold, Descriptive Geology, 

234, 235; [/. S. Geol. Expl. of 40th 

Parallel, 331, 337, 339, 362, 370; 

Absaroka Folio U. S. Geol. Surv., 337. 
Hall, A. D., The Soil, 14, 19, 39, 52, 63, 

65, 83, 90, 93, 94; The Fertility of the 

Soil, 75, 76, 77, 88. 
Hall and Bolster, Surface Water Supply 

of U. S., 612, 614. 
Hamilton Inlet, and spruce forest belt 

of Canada, 570. 
Hann, J., Handbook of Climatology, 8, 

S6, 148. 



Harney-Malheur System, Oregon, 198. 

Harney Peak, 441. 

Harper, R. M., Contr. Dept. Bot. Colum. 

Univ., 542. 

Harrison and Williams, Jour. Am. 
Chem. Soc, 11. 

Hayden, F. v., U. S. Geol. and Geog. 
Surv. of Terr., 277, 279, 280, 290, 367, 
382; gih Ann. Kept. U. S. Geol. ajid 
Geog. Surv. of Terr., 281; U. S. Geol. 
and Geog. Surv. of Col. and Adj. Terr., 

365- 
Hayes and Campbell, Geomorphology 

of the Southerri Appalachians, 591. 
Hayes and Kennedy, Oil Fields of 

Texas-Louisiana Gulf Coastal Plain, 

53°- 

Hayes and Ulrich, The Columbia Folio 
U. S. Geol. Surv., 705. 

Hayes, C. W., Physiography of the Chat- 
tanooga District in Tennessee, Georgia, 
and Alabama, ^'91; Sewanee Folio U. S. 
Geol. Surv., 698. 

Hay Fork Valley, 142. 

Henry, A. J., Climatology of U. S., 112, 
147, 179, 584, 645. 

Henry Mountains, relation to Kaiparo- 
wits Plateau, 264; relief map of, Fig. 82, 
p. 291; vegetation of, 292. 

Hetch-Hetchy River, 170. 

Highland Rim, 695, 696, 697, 704. 

HiGHLANTJS OF New Jersey, relation to 
Newer Appalachians province, 666. 

High Plains, relation to Llano Estacado, 
408; structure and history of, 417; 
local storm floods of, 417; structure of 
Tertiary deposits of. Fig. 151, p. 418; 
typical view of, in W. Kansas, Fig. 152, 
p. 418; physical development of, 419; 
dift'erential uplift in, 420; present 
character of stream work in, 420; 
border topography of, 421; local bad- 
land topography of, 421; eastern border 
in Texas and Oklahoma, 421; typical 
border topography of. Fig. 153, p. 422; 
"The Breaks" of, 422; erosion es- 
carpment of. Fig. 154, p. 422; details 
of form, eastern border of, Fig. 155, 
p. 423; sand hills and lakes of, 423; 
" blow-outs " of, 423; rainfall of, 424; 
precipitation in the Texas region. Fig. 
156, p. 424; vegetation of, 425. 

High Plateaus of Utah, topography 
of, 260; members of, 262; relief features 
of. Fig. 72, p. 262; San Rafael Swell of, 

273- 
High Sierra, 170. 
HiGHwooD Mountains, and Keewatin 

ice sheet, 412; topography of, 449; 

stream flow and vegetation in, 449; 

map of, Fig. 168, p. 450. 



INDEX 



743 



HiLGARD AND LouGHRiDGE, Classifica- 
tion of Soils, 1 06. 

HiLGARD AND Weber, Bull. Cal. Agri. 
Ex. Sta., 97. 

HiLGARD, E. W., Soils, 12, 20, 27, 29, 30, 

37, 38, 59- 68, 69, 71, 72, 75, 79, 81, 85, 
88, 94, 96, 97, 98, 100, 105, 180, 524, 
542; Agriculture and Geology of Missis- 
sippi, 523, 542; Science, 534; see 
Dedication. 

Hill and Vaughan, Nueces Folio U. S. 
Geol. Surv., 432. 

Hill, R. T., Physical Geography of Texas 
Region, 390, 393, 395, 398, 408, 417, 
434; Geography and Geology of Black 
and Grand Prairies, Texas, 434, 492. 

Hills, R. C, Spanish Peaks Folio U. S. 
Geol. Surv., 361; Elmoro Folio U. S. 
Geol. Surv., 397. 

Hitchcock, C. H., Final Report on Geology 
of Massachusetts, 502; Controlling Sand 
Dunes in U. S. and Europe, 504; Geology 
of the Hanover Quadrangle, 539; Geology 
of New Hampshire, 643; Geological Sur- 
vey of New Hampshire, 647; Recent 
Landslide in the White Mts., 647 ; Geology 
aiul Topography of White Mts., 648; 
Geology of New Hampshire, 648; Glacial 
Markings Among the White Alts., 648; 
Glaciation of the Green Mt. Range, 649, 
651. 

Hiwassee River, gorge of, 610; direc- 
tion of, 668. 

HoLSTON River, power of, 612. 

Honey Lake, 172. 

HoosAC Mountains, relation to Green 
Mts., 636. 

HoosATONic River, valley of, 639, 681. 

Hoosic Valley, 681, 682. 

Horizontal Expansion, of rock, rate of 
with changing temperature, 15. 

Hot Springs, Tennessee, gorge at, 610. 

Howe, Ernest, Landslides in San Juan 
Mts., 375- 

Hozomeen Mountains, terminating cas- 
cades, 156; composition of, 157; physio- 
graphic features of, 158; glacial erosion 
of, 161; climatic conditions, 165. 

HuACHUCA Mountains, tree growth, 
249. 

HuALPi Valley, 269. 

Hudson Bay Basin, soil erosion on, 13. 

Hudson Bay, paleozoic sediments near, 
561; spruce forest west of, 570. 

Hudson Bay-St. Lawkence Divide, 
surface of, 559. 

Hudson Valley, middle, 665, 681, 683. 

HuEco Basin, 399. 

Humboldt Lake, relation to Lake La- 
honton, 214; Post-quaternary fault on 
southern shore of, 226. 



Humidity, average annual, of air in U. S., 
Fig. 21, p. 119. 

Humus, sources and plant relations, 77; 
porosity of, 79; density of, 79; amount 
and derivation of, 80; in relation to 
root development, 81; definition of, 82; 
determination, Grandeau method for, 
83; chemical composition of, 83; raw, 
consists of, 85; action of fungi on, 93; 
nitrogen of in humid and arid regions, 
96; amount of in humid and arid 
regions, 97. 

Hunter Mountain, 691. 

Huntington ant3 Goldthwait, Hurri- 
cane Fault in Toquerville District, 283. 

Huntington, E., The Pidse of Asia, 59. 

Huron River, 483. 

Hurricane Ledge, length of, 109. 

Hydration, as a process, 10; effects of, 10. 

Hygroscopic Water, value of, 54. 

Idaho, volcanic dust in, 17, 24; north- 
central, mountains of, 320; central, 
canyons in, 322; subdivisions of moun- 
tains of, 323. 

Illinoian Glacial Stage, 466, 467. 

Illinois Valley, 142. 

Imperial Canal, 240. 

Imperial Valley, Salton Sink region, 
240. 

Indus Valley, melting of snow in, 59. 

Interior Plateau, of British Columbia, 
159; and Frazer River, 160. 

Intermontane Trenches, glacial ero- 
sion in, 300; east-west section, Fig. 87, 
p. 301; definition of, 301. 

Inyan Kara, 445. 

lowAN Glacial Stage, 466, 468. 

Iron, as soil element, 68. 

Iron Mountains, direction of, 607. 

Irrigation, map of the West, Fig. 48, 
p. 189; along Colorado River, 240. 

Irving, R. D., Geology of Wisconsin, 497. 

ISLANT) Lake, and transcontinental spruce 
forest, 570. 

Isle' OF Palms, sand dunes of, 504. 

IVANHOE, 610. 

Jack's Mountain, 677. 

Jaggar and Palache, Bradsliaw Mts. 
Folio U. S. Geol. Surv., 253. 

Jail Rock, Fig. 153, p. 422. 

Jamaica Plain, Mass., forest growth on 
steep and rocky hillside of, 652. 

James Bay, 561, 570. 

Jamieson, , Rept. Agri. Research 

Ass7i. of Northeastern Counties of Scot- 
land, 92. 

Jeff Daws or Wheeler Peak, 233. 

Jefferson, Mark, Geography of Lake 
Huron at Kincardine, Ontario, 485. 



744 



INDEX 



Jefferson Range, in southwestern Mon- 
tana, 315; character of sections of, 315. 

Jensen, C. A., Some Mutual EJfecls of 
Tree Roots a>id Grasses on Soils, 76. 

JiCARiLLAS, The, 390. 

Johnson, D. W., The Southernmost Gla- 
ciation in f/. 5., 138; ^ Recent Volcano 
in San Francisco Mountain Region, 273; 
Volcanic Necks of Mount Taylor Region, 
283, 296; Profile of Maturity in Alpine 
Glacial Erosion, 312; The High Plains, 
418, 420; Tertiary History of the Ten- 
nessee River, 669. 

Johnson, E. R., Sources of American 
Railway Freight Traffic, 612. 

jornado del muerto bolson, 399. 

Jupiter Inlet, 546, 547. 

Jura River, profile of, 172. 

Kaibab Plateau, elevation of, 268; 

topography of, 271; altitude compared 

with that of San Francisco Plateau, 

273; climate of, 288; forests of, 289. 
Kaiparowits Plateau, topography of, 

264; vegetation of, 264. 
Kanab Creek, Utah, torrent conditions 

in, 7; direction of, 261. 
Kanab Plateau, and Kanab Creek, 261; 

topography of, 270; relation to Kaibab 

Plateau, 271. 
Kanawha River, power of, 612; canyon 

of, 694. 
Kansas Glacial Stage, 466, 467. 
Karst of Austria, forests of, 47. 
Kaweah River, 182. 
Kazan River, and transcontinental 

spruce forest, 570. 
Kearn, lake, 184; river, 184. 
Keeler, H. L., Our Native Trees, 42. 
Keewatin Ice Sheet, and Prairie Plains, 

465; center of ice accumulation. Fig. 

176, p. 465. 
Keith, A., Pisgah Folio U. S. Gcol. Surv., 

604; Geology of the Catoctiti Belt, 623; 

Wartbiirg Folio U. S. Geol. Surv., 698. 
Kellermann, K. F., Functions and 

Value of Soil Bacteria, 86, 92. 
Kellogg, S. B., Problem of the Dunes, 

504, SOS- 
Kemp, J. F., Physiography of the Adiron- 

dacks, 583. 
Kendrick Mountain, 296. 
Kerner von Marilaun, a., Die Ab- 

hdngigkeit der Pflanzengestalt von Klima 

■und Boden, 62. 
Kettleman Hills, and Lake Tulare, 

184. 
Keyes, C. R., Rock Floor of Intermoni 

Plains of Arid Regions, 237, 399. 
King, Clarence, U. S. Geol. Expl. of 

40th Par.. 362. 



King, F. H., Physics of Agriculture, 27; 
The Soil, 56, 57, 73; Productivity of 
Soils, 429. 

Kings River, 1S2. 

Kisatchie Cuesta, 533. 

KiSHicoQuiLLis Valley, 677. 

Klamath Mountains, subdivisions of, 
138; boundaries. Fig. 28, p. 141; valleys 
of, 143; and Pacific Coast downfold, 
177; and plain of erosion, 182. 

Klail4th River Valley, 143. 

Kootenai Valley, 300. 

Koppen's classification of climate in re- 
lation to vegetation, Fig. 13, p. iii. 

Kuba Table, 414. 

Labrador Ice Sheet, and Prairie Plains, 

46s; center of ice accumulation. Fig. 

176, p. 465. 
Labrador Peninsula, elevations of 

margin and interior, 559. 
Ladd, E. F., Bull. So. Dakota Agri. Exp. 

Station, 79. 
Ladd, S. B., U. S. Geog. and Geol. Surv. 

of Colorado and Adj. Terr., 278, 362, 

370- 

Ladore Gate, 346. 

Lahonton, Lake, 214. 

Lake George, 581, 583. 

Lake Huron, sand dunes east of, 505; 
situation of on ancient coastal plain, 
561. 

Lake Mackay, and transcontinental 
spruce forest, 570. 

Lake MANnTOBA, 410. 

Lake Michigan, and preglacial drainage, 
476; profile across, Milwaukee to 
Grand Haven, Fig. 184, p. 476; sand 
dunes at southern end of, 505; situa- 
tion of on ancient coastal plain, 560. 

Lake Mistassini, 569. 

Lake Nipissing, 562. 

Lake Okechobee, 545, 549. 

Lake Ontario, Niagara escarpment near, 
560. 

Lake Osborn, 547. 

Lake Plains, extent of, 477; origin of, 
477; relation to proglacial lakes, 477. 

Lake St. John, view of. Fig. 227, p. 568; 
outlet of, 568. 

Lake Temiskaming, 561, S62, 567. 

Lake Winnipegosis, 410. 

Lake Winnipeg, plains near, 410; 
Niagara escarpment west of, 560. 

Lampasas Plain, Texas, summits of. 
Fig. IS9, p. 432; plateau remnants, 
434; a divide of, Fig. 161, p. 435. 

Langville, H. D., (and others). Forest 
Conditions in Cascade Range Forest 
Reserve, Oregon, 162. 



INDEX 



745 



La Plata Mountains, origin of, 277; 
relief of, 376; western summits of, 
Fig. 128, p. 377; vegetation of, 378. 

La Plata Valley, looking down from 
head of. Fig. 127, p. 377. 

Laramie Mountains, topography of, 
331; timber growth of, 331; and Pine 
Ridge, 405. 

Laramie Plains, view from Mandel, 
Fig. 107, p. 338 ;_ topography of, 339. 

Larix, decidua, soil requirements of, 42; 
sibirica, soil requirements of, 42; lara- 
ci)ia, soil requirements of, 42. 

La Rue and Henshaw, Surface Water 
Supply of the U. S., 216, 217. 

Lassen Peak, volcanic ridge, 156; dis- 
trict and plain of erosion, 182. 

Las Vegas Mesa, 395, 397, 401. 

Later Wisconsin Stage, of glacial 
period, 466, 468. 

Lauderback, G. D., Basin Range Struc- 
ture of Humboldt Region, 221. 

Laurentlan Plateau, moss cover and 
run-off, 5; topographic features of , 554; 
rock types and boundaries of, Fig. 222, 
p. 554; outline of in U. S., 555; topo- 
graphic imity of, 555; dominating feat- 
ure of, 555; view of in Labrador, Fig. 223, 
p. 556; differences in elevation of, 556; 
uplifted peneplain of, 557; lakes of, 557; 
glacial features of, 557; representative 
districts of, 558-560; border topography 
of 560; streams of, 561; the Nipigon 
district of, 562; changes of level of, 563; 
evidences of change of level of, 563; 
lake region of, 564; abundance of 
lakes in, 564; map of lake region of. 
Fig. 225, p. 565; details of drainage in 
a limited portion of, Fig. 226, p. 566; 
causes of abundance of lake basins in, 
567; types of lakes in, 567; view on 
shore of Lake St. John, Fig. 227, p. 
568; longevity of lakes of, 569; vegeta- 
tion of, 569; Superior Highlands of, 
572-578; Adirondack Mountains of, 

578-584- 

Laurentide Mountains, relation to 
Laurentian Plateau, 556; view of. 
Fig. 224, p. 558; streams of, 558. 

Lava, of Columbia and Snake rivers, 
age of, 194. 

Lava Fields of the Northwest, Fig. 49, 
p. 192. 

Lawson, a. C. (and others). The Cali- 
fornia Earthquake of April 18, 1906, 
128, 130, 131, 132, 135; Geomorphogeny 
of Coast of Northern California, 133, 134, 
135; Bull. Dept. Geol., Univ. Cal., 183. 

Lay, H. C, Trans. Arner. Inst. Mining 
Engineers, 375. 

Lebanon Valley, 666. 



Lee's Ferry, 276. 

Lee, W. T., Geology and Water Resources 
of Owen's Valley, Cal., 168; Geologic 
Reconnaissance of Part of Western 
Arizona, 238, 254; Water-Supply Paper 
U. S. Geol. Surv., 401. 

Leiberg, J. B., Forest Conditions in the 
Absaroka Division of the Yelloivstone 
Forest Reserve, 5, 335; Forest Conditions 
in the Northern Sierra Nevada, Cal. ,171; 
Priest River Forest Reserve, 305; Bitter- 
root Forest Reserve, 326, 327. 

Leiberg, Rixon, Dodwell, and Plum- 
MER, Forest Conditions in San Fran- 
cisco Mts. Forest Reserve, 295, 296. 

Leucite Hills, 338, 342. 

Leupp Echo Cliffs, 276. 

Leverett, Frank, Comparison of North 
American and European Glacial De- 
posits, 467, 468, 488; The Illinois 
Glacial Lobe, 475, 486; Outline of 
History of Great Lakes, 476; Glacial 
Formations and Drainage Features of 
Erie and Ohio Basins, j^tj; An Instance 
of Geographical Control tipon Human 
Afairs, 486. 

Lewis Range, of northern Rockies, 298; 
and longitudinal trenches, 302; eastern 
border features of, 307; relation of 
topography to structure in, 310; map 
of part of. Fig. 94, p. 311; glacial forms 
in, 312; pyramidal moimtains of, 312; 
Mount Gould, Fig. 95, p. 313; origin 
of cirques in, 314. 

Lewiston, gorge near, 196. 

Lights Canyon, 172. 

Limestone, fresh, analyses of, 729. 

LiMiTAR Range, 391. 

Lincoln Forest Reserve, trees in, 403; 
range of timber species in, Fig. 145B, 
p. 404. 

Lindgren and Drake, Silver City Folio 
U. S. Geol. Surv., 323. 

Lindgren and Turner, Marysville Folio 
U. S. Geol. Surv., 182. 

Lindgren, Groton, and Gordon, Ore 
Deposits of New Mexico, 403. 

Lindgren, W., Colfax Folio U. S. Geol. 
Surv., 173; Sacramento Folio U. S. 
Geol. Surv., 173; Pyramid Peak Folio 
U. S. Geol. Surv., 173; Geological Recon- 
naissance Across the Bitterroot Range 
and Clearwater Mts. in Montana and 
Idaho, 193, 302, 321, 322, 323, 326; 
Gold Belt of Blue Mts. of Oregon, 193, 
209; Gold and Silver Veins of Silver 
City, De Lamar, and Other Mining 
Districts, Idaho, 197, 198, 206, 323, 
324; Prof. Paper U. S. Geol. Surv., 
No. 27, 304. 

Line Moltntain, 673. 



746 



INDEX 



LiNNiTLLE Rii'ER, valley of, 6io; capture 
of feebler stream by, 619. 

LiTHOSPHERE, average composition of, 64. 

Little Belt Mountains, outline and 
relief of, 446; structure of, 446; topo- 
graphic map of. Fig. 167, p. 447; 
climate of, 448; soil of, 448; vegetation 
of, 448; slope exposure and tree growth 
in, 448. 

Little Churchill River, 557. 

Little Colorado River, 272, 274, 275. 

Little Hoosic Valley, 681. 

Little Missouri Buttes, 445. 

Little Rock, location in fall line, 499. 

Little Rocky Mountains, and Kee- 
watin ice sheet, 412; topography of, 
449; structure of, 451. 

Little Sacramento Valley, 140. 

Little Tennessee River, gorge of, 610; 
power of, 612. 

Little Valley, 171. 

Livingston Range, of northern Rockies, 
298; and longitudinal trenches, 302; 
extent of, 308; relation of topography 
to structure in, 310. 

Llano Estacado, surface of, 408; topo- 
graphic and drainage features of, 417; 
and Edwards Plateau, 431; relief map 
of. Fig. 158, p. 431. 

Loam, defined, 34. 

Loblolly Pine, water requirements of, 
50; growth of in Coastal Plain, 530. 

Lockesburg Cuesta, 533. 

Lock Mountain, 673. 

Loess Deposits of Prairie Plains, 
occurrence of, 488'; origin of, 488. 

Logan's Gap, 677. 

Long Island, soil erosion on, 6; general 
geography of, 506; length of, 506; 
glacial topography of,_ 507; terminal 
moraines on, 507; relative positions of 
ice during the two stages of the Wis- 
consin glaciation. Fig. 195, p. 507; 
section showing relation of outwash to 
terminal moraine. Fig. 196, p. 508; 
outwash plains of, 508, Fig. 197, p. 
509; topographic features related to 
structure of, 509; cross section of, 
Fig. 198, p. 509; soil types of, 510; ter- 
minal moraines, soils and vegetation of. 
Fig. 199, p. 511; characteristic growth 
of pitch pine and scrub oak. Fig. 200, 
p. 512; effects of repeated fires on soil 
and vegetation. Fig. 201, p. 512; 
typical growth of hardwood on clayey 
portions of Harbor Hill moraine, Fig. 
202, p. 513; scattered growth of pitch 
pine and scrub oak on sandy portion 
of Ronkonkama moraine, Fig. 203, 
p. 513; natural vegetation of, 514. 

Lookout Mount.\ins, 666, 695, 696. 



Los Angeles, 177. 

Lost River Mountains, 198, 207. 

Loughridge, R. H., Rept. Cal. Exp. 
Sla., 53. 

Louisiana-Texas Section of Coastal 
Plain, outer border of, 529; coastal 
features of Texas, Fig. 211, p. 529; soils 
of, 530; vegetation of, 530; loblolly 
pine in, 530; physiographic devel- 
opment of, 531; prominent topo- 
graphic features of the Gulf Coastal 
Plain, Fig. 212, p. 532; mounds of, 
533; cross section of in Louisiana and 
southern Arkansas, Fig. 213, p. 533; Red 
River rafts in, 534; lakes of Red River 
valley in. Fig. 215, p. 535; timber 
deadened in temporary raft lake. Fig. 
216, p. 536; one of the- Red River 
rafts in, Fig. 217, p. 536; map showing 
typical drainage features in Red River 
and Mississippi River flood plains, 
Fig. 218, p. 537; growth and drainage 
of raft lakes. Fig. 219, p. 538. 

Low, A. P., The Mistassinni Region, 559; 
Report on Explorations in James Bay 
and Country East of Hudson Bay, 559. 

Lowell, Percival, Plateau of San Fran- 
cisco Peaks in its Effects on Tree Life, 

293- 

Lower Ausable Lake, 581. 

Lower Austral Province, character- 
istics of, 123. 

Lower Colorado Basin, proportion of 
mountains and plains in, 236; floors of, 
236; "lost rivers" of, 237; types of 
lowlands of, 237; special drainage fea- 
tures of, 210, 238; climate of, 243; soil 
of, 243; vegetation of, 244; topographic 
profile in relation to rainfall. Fig. 81, 
p. 286. 

LowLANT) OF Central New York, re- 
sources of, 707; geologic map of, 707; 
physiographic belts in, Fig. 284, p. 708; 
topographic features of, 709; Finger 
Lakes of, 709; map of portion of, Fig. 
285, p. 710; abandoned channels of, 
711; proglacial lakes in Finger Lake 
district of, Figs. 286, 287, p. 712; 
Fig. 288, p. 713; channels and deltas 
of a part of the ice-border drainage 
between Leroy and Fishers, Fig. 289, 
p. 714; channel features of, 715; gulf- 
channel north of Skaneateles, Fig. 290, 
p. 715; Niagara Falls in, 716; drumlin 
types in, 716; drumlin belts of, 716; 
topographic types in. Fig. 292, p. 718; 
types of drumlins of, 719; formation of 
drumlins in, 720. 

LoYALSocK Creek, 670. 

Lukachukai Mountains, 275. 

Lycoming Creek, 670. 



INDEX 



747 



MacDonald Range, and longitudinal 

trenches, 302. 
Macdougal, D. T., Across Papagueria, 

, 245- 

Macon, location in fall line, 499. 
Made Land, 724. 

Madison Range, in southwestern Mon- 
tana, 315. 
Magdalena Range, 391, 402. 
Magnesium, as soil element, 70. 
Mahanoy Mountain, 673. 
Malheur Lake, Oregon, South Shore 

of, Fig. SI, P- 197- 

Manhantango Mountain, 673. 

Manhattan Prong, 632. 

Manzano Mountains, 389, 391. 

Marble Canyon, 261, 285. 

Marbut, C. F., Physical Features of 
Missouri, 454; The EvoliUion of the 
Northern Part of the Lowlands of South- 
eastern Missouri, 528. 

Marcou Buttes, 292. 

Marias River, 414. 

Marine Temperature Influences, on 
the Atlantic coast, 112; on the Pacific 
coast, 112. 

Markagunt Plateau, direction of, 260; 
location in High Plateaus, 262; topog- 
raphy of, 264; vegetation of, 265; 
surface of, 265. 

Marsh, 725. 

Marsh Pass, Arizona, 275. 

Martha's Vineyard, former condition 
of, 502; diagrammatic section of. Fig. 
194, p. 506; physiographic features of, 
506. 

Maryland Section of Coastal Plain, 
swamps on divides of, Fig. 205, p. 517. 

Marysville, and Yuba River, 182; 
forest conditions in region of, 320. 

Mato Tepee, 445. 

Matson and Clapp, 2d Ann. Kept. Fla. 
Geol. Surv., 545, 553. 

Matson, G. C., Water Resources of the 
Blue Grass Region of Kentucky, 701, 702, 

703- 
Matthes, F. E., Cliff Sculpture of Yosem- 

ite Galley, 170; Glacial Sciilpture of 

Bighorn Mts., 354. 
Maumee River, 483. 
McCloud Valley, 140. 
McFarland, R., Beyond the Height of 

Land, 570. 
McGee, W. J., Sheet-flood Erosion, 236; 

The Lafayette Formation, 502; Geology 

of the Head of Chesapeake Bay, 515. 
Meadow^, 725. 
Mearns, E. a.. Mammals of Mexican 

Boundary of U. S., 240, 243, 245, 249, 

250. 



Medicine Bow Mountains, situation in 
Rocky Mts., 329; topography of, 337; 
glacial features of, 337; forests of, 337; 
relation to Laramie Plains, 338. 

Mendenhall, W. C, Hydrology of San 
Bernardino Valley, 46, 95; Ground 
Waters and Irrigation Enterprises in 
Foothill Belt, Southern California, 135, 
136; Development of Underground Water 
in Western Coastal Plain Region of 
Southern California, 186. < 

Mendocino County, Cal., sand dunes 
of, 504. 

Merced River, 170. 

Merriam, C. H., Life Zones and Crop 
Zones of U. S.,iii; Results of Biological 
Survey of San Francisco Mountain 
Region in Arizona, 293; Geological Dis- 
tribution of Life in North America with 
Special Reference io -Mamma/ ia, 493, 553 ; 
Geological Distribution of Animals and 
Plants in North America, 553; Mammals 
of the Adirondack Region, 584. 

Merrill, G. P., Rocks, Rock-weathering 
and Soils, 15, 16, 25, 84, 204; Stones 
for Building and Decoration, 16. 

Mesa de Maya, structure of strata 
underneath. Fig. 141, p. 395; topog- 
raphy of. Fig. 142, p. 396; basalt 
flows of, 396; and strata of Great 
Plains, 408. 

Mesa Verde, southwestern Colorado, 
Fig. 71, P- 259. 

Mettawwe Valley, 682. 

Michigamme Mountain, slight eleva- 
tion of, 575. 

Meddle Park, 382. 

Miller, W. J., Trough Faulting in the 
Southern Adirondacks, 581. 

MiMBRES Range, 390. 

Mimbres River, 246. 

MiNAS Basin, 626. 

Mississippi River, old and new channels 
of. Fig. 183, p. 475. 

Mississippi Valley, loess deposits, 24. 

Mississippi Valley Section of Coastal 
Plain, " black prairies " of, 525; 
" Reelfoot Lake district " of, 525; 
finger-like extensions of the Mississippi 
delta, Fig. 209, p. 525; lowlands in, 
526; floods in, 526; extent of protective 
works in, 526; relation of river control 
to forestry, 526; lower alluvial valley 
of the Mississippi, Fig. 210, p. 527; 
topographic features of, 528; drainage 
of, 528. 

Missouri River, headwaters of, 409; 
effects of glaciation on course of, 475. 

Moencopie River, 275. 

Mogollon Mesa, and surface of San 
Francisco Plateau, 273; section of, 



748 



INDEX 



Fig. 76, p. 273; junipers on, 287; forma- 
tion of, 292; topography of, 296; vege- 
tation of, 297. 

MoGOLLON Mountains, section of. Fig. 
76, p. 273; mesa forest of western 
yellow pine in, Fig. 84, p. 295. 

Mohave Desert, 184, 237. 

MoHAVv'K Mountains, 245. 

MoHR, Charles, Plant Life of Ala- 
bama, 542. 

Moki-Navajo Country, topography of, 
274; vegetation of, 276; structural 
features of, 275. 

Monadnock, definition of, 609. 

Mono Lake, 167, 168. 

MoNOMOY Point, wave action on, 503. 

Montague Lake, 643. 

Montana, section of front ranges in, 
Fig. 91, p. 307; map of Great Plains 
and front ranges. Fig. 92, p. 308; hog- 
back type of mountains border, Lewis 
and Clarke National Forest, Fig. 9, 
p. 309; western, minor ranges of, 317; 
western, forest distribution in, Figs. 
99, 100, p. 318; influence of slope ex- 
posure on water supply and forests, 

319- 

Monterey, bay of, 176. 

Monterey County, Cal., sand dunes of, 
504- 

Montezuma Range, trees of, 234. 

Montgomery, location in fall line, 499. 

Moses Lake, 201. 

Mount Adams, height of, 645. 

Mount Baker, district, 158; and western 
portion of Skagit Mountains, Fig. 36. 
p. 159; age of, 160; slopes of, 459. 

Mount Chopaka, 156, 157. 

Mount Dellenbaugh, 258, 269. 

Mount Ellen, 292. 

Mount Ellsworth, 292. 

Mount Emma, 258. 

Mount Evans, 369. 

Mount Greylock, 681. 

Mount Hitlers, 292. 

Mount Hood, relief map of, Fig. 37, p. 
161 ; glacier systems of, 162. 

Moltnt Jefferson, height of, 645. 

Mount Katahdin, exception to plateau 
features of the province, 636; relation 
to White Mountain district, 646; 
former local glaciers on, 648. 

Mount Madison, height of, 645. 

Mount Mitchell, height of, 603; com- 
pared with Mount Washington, 645. 

Mount Monadnock, exception to pla- 
teau feature of the province, 636; ele- 
vation of, 637; relation to White 
Mountain district, 646. 

Mount Monroe, height of, 645. 

Mount Nebo, 266. 



Mount Pennell, 292. 

Mount Rainier, glacier systems of, 162. 

Mount Scott, slopes of, 459. 

Mount Taylor, and relief of Colorado 

Plateaus, 258; peneplain in region of, 

283; junipers on, 287; study of, 291; 

extinct volcano, 292; topography of, 

296; tree growths on, 297. 
Mount Toby District, Massachusetts, 

648. 
Mount Trumbull, 258, 270. 
Mount Wachusett, relation to other 

Monadnocks, 637; relation to White 

Mountain district, 646. 
Mount Washington, height of, 645. 
Mount Webster, 647. 
Mount Whitney, height of, 170. 
Mount Willey, 647. 
Mount Wilson Group, Fig. 129, p. 379. 
Muck, 724. 
Mule River, 198. 
MuLLER, , NatUrliche Humusfor- 

men, 85. 
MuNCY Creek, 670. 
Murray, Sir John, Origin and Character 

of the Sahara, 98. 
Music Mountain, 269. 

Nacimiento Range, 391. 

Nantahala River, gorge of, 610. 

Nantucket, former condition of, 502; 
relief and drainage of, 505. 

Nashville Basin, section across. Fig. 
283, p. 704; topography of, 705; soil of, 
705; " barren lands " of, 706. 

Natchitoches, 534. 

Navajo Mountain, 276. 

Navajo River, 275, 374. 

Needle Mountains, volcanic rocks of, 
378; part of, Fig. 130, p. 380; glacial 
features of, 381. 

Nehalem River, 143. 

Nelson, S. A., Meteorology of Mount 
Washington, 645. 

New England Mountains and Pla- 
teaus, upland plain of, 637; cretaceous 
and Tertiary peneplains of, 637; profile 
across central New England, Fig. 260, 
p. 637; dissection of, 638; geologic 
features of, 638; effects of glaciation on, 
640; topographic and drainage modifi- 
cations on, 640; till deposits of, 640; 
rock outcrops of, 640; glacial deposits 
of, 641; eskers of, 641; delta plains of, 
642; sand plains of, 642; stream terraces 
in, 642; lakes of, 643; percentage of 
lake surface in, 643; relation of lakes 
to run-off, 644; subregions of, 645-664; 
forest growth on steep and rocky hill- 
side. Fig. 262, p. 652. 

New England, soil erosion in, 6, 



INDEX 



749 



Newer Appalachians, divisions of, 588; 
relief map of central part of Appalach- 
ian System, Fig. 268, p. 665; southern 
district of, 666; ridges of, 667; early Ter- 
tiary peneplain of, 667; stream types in, 
668; t^'pes of drainage in, 669; central 
district of, 670-679; distinctive features 
of topography in, 671; half-cigar- 
shaped mountains developed on hard 
rock, Fig. 269, p. 674; canoe-shaped 
ridges of hard rocks, Fig. 270, p. 674; 
development of anticlinal valleys and 
synclinal mountains, Fig. 271, p. 676; 
varying positions of plane of base- 
leveling to hard and soft strata, Fig. 
272, p. 677; drainage features of, 678; 
modification of drainage of, 678; 
northern district of, 679-683; cross 
section from Hudson Valley across 
Rensselaer Plateau and Taconic Range, 
Fig. 273, p. 680; geologic and physio- 
graphic map of the Taconic region. 
Fig. 274, p. 680; tree growth of, 683. 

New Jersey Section of Coastal Plain, 
inner and outer lowlands of, 515; sand 
reef, salt marsh, and coastal plain up- 
land of, Fig. 204, p. 515. 

New River, in Appalachian System, 
610; power of, 612; South Fork of, 619. 

New River, in Salton region, 240. 

New York, terminal moraine and direc- 
tion of ice movement in vicinity of. 
Fig. 258, p. 632. 

Niagara Escarpment, 560, 709. 

Niagara Falls, 716. 

Niobrara and Loltp Rivers, forests and 
stream flow in basins of, 6. 

NiPiGON District of Laurentian Pla- 
teau, topography of, 562; scenery of, 
562. 

Nitrate of Soda, in deserts, loi. 

Nitric Acw, amount in drain water, 12. 

Nitric Ferment, from soil from Cito, 
Fig. 10, p. 91. 

Nitrogen, brought to surface of earth 
by rain, 77; rare essential plant food, 
78; changes in soil produced by bac- 
teria. Fig. 9, p. 89; direct fixation of 
from soil air by bacteria, 90; free, ap- 
propriated by forests by trichomes, 93; 
of soil humus in humid and arid regions, 
96. 

Nitrous Ferment, from soil from Cito, 
Fig. 10, p. 91. 

Nittany Valley, size of, 677. 

Noble, L. F., Contributions to Geology 
of Grand Canyon, Arizona, 284, 285, 
286, 288, 289. 

NoLiCHUCKY River, gorge of, 610; power 
of, 612; fate of tributary of, 619. 

North Branch, 670. 



North Carolina, rainfall of western 
mountain ranges, 121. 

Northern Cascades, and 49th parallel, 
156, 159; glacial features of, 161; rain- 
fall of, 164; forests of, 164. 

Northern Great Plains, topographic 
development of, 410; glacial features 
of, 412; map of glacial features of, Fig. 
148, p. 412. 

Northern Rockies, boundaries of, 298; 
subdivisions of, 298; mountain systems 
and ranges and intermontane trenches, 
Fig. 85, p. 299; location map of part of. 
Fig. 86, p. 299; intermontane trenches 
of, 300; geologic features of, 302; cli- 
matic features of , 3 26 ; vegetation of , 3 26. 

Northern Sierras, characteristic species 
of trees, 174; ranges of four character- 
istic species of trees. Fig. 42, p. 175. 

North Haven Sand Plain, 661. 

North Park, 382. 

North Table Mountain, 361. 

Oatka Valley, 713. 

OcATE Mesa, 397. 

OcATE Plateau, 395. 

Ogden Canyon, 227. 

Ogilvie, I. H., Glacial Phenomena in the 
Adirondacks and Champlain Valley, 580. 

O'Harra, C. C, Badland Formations of 
Black Hills Region, 416. 

Ohio River, effects of glaciation on 
course of, 475. 

Okanogan Mountains, extent of, 156; 
composition of, 157; glaciers of, 157; 
peaks of, 159; and the plain of the 
Columbia, 202. 

Okanogan Valley, 201, 301. 

Older Appalachians, divisions of, 588; 
southern division of, 603-635; northern 
division of, 636-664. 

Olympic Mountains, height of, 144; 
forests of, 144; and timber hne, 163. 

Onont)aga Valley, 713. 

Open Range in the West, approximate 
location and extent of. Fig. 62, p. 231. 

Oppokov, E. v., nth International Navi- 
gation Congress, 53. 

Oraibi, 283. 

Oregon, volcanic dust in, 17, 24; coast 
ranges of, 142; Cascade Mountains, 
topographic profile in relation to rain- 
fall. Fig. 38, p. 163; timber of, 163; 
sketch map of southeastern part. Fig. 

52, p- 199- 
Organ Range, 391. 
Osage Prairie, appearance of, 461; 

relief of, 463. 
OscuRA Mountains, 391. 
OsoYoos Lake, 154. 
Ottawa River, 561. 



750 



INDEX 



Ouachita Mountains, topography of, 

456- 
Overlook Mountain, ledges at, 691. 
Owen's Lake, 167. 
Owen's Valley, 168. 
Owl Creek Range, trend compared to 

Uinta's, 345; relation to Bighorn 

Mountains, 349. 
Owyhee Range, 202. 
Oxidation, in rocks, 8; extracellular, by 

plant roots, 20. 
Oxygen, as soil element, 66. 
Ozark Province, subdivisions of, Fig. 

169, p. 452; rehefs of, 452; structure of, 

452; topography of, Fig. 170, p. 453; 

section across, Fig. 171, p. 454; broad 

topographic features of, 454; soils and 

tree growth in, 455. 
Ozone, 8. 

Pacific Coast Downpold, 177. 

Pacific Coast Valleys, general geog- 
raphy of, 177; soils of, 188. 

Pacific Forests, trees of, distribution 
of, 125. 

Packard, A. S., Evidences of the Existence 
of Ancient Local Glaciers in White 
Mountain Valleys, 648. 

Padre Island, length of, 529. 

Pahute Canyon, 275. 

Palms, 186. 

Panamint Range, 228. 

Panamint Valley, 228. 

Panguitch Lake Buttes, 292. 

Paria Plateau, topography of, 264; 
vegetation of, 264. 

Paria River, 261. 

Park Range, rehef of, 370; tree growth 
of, 370; extent of former glacier sys- 
tems in parts of, Fig. 125, p. 371. 

Parks of the Southern Rockies, 381- 
385; types of, 385; tree zones and 
types in, 386. 

Pasayten, river, 156, 161; valley, 165. 

Pasquia Hills, 410. 

Passarge, S., Die Kalahari, 17. 

Path Valley, size of, 677. 

Patten, H. E., Heat Transference in 
Soils, 61. 

Patterson, coulees near, 200. 

Paunsagunt Plateau, location in High 
Plateaus, 262; relation to Markagunt 
Plateau, 264; topography of, 265. 

Pavant Plateau, 262. 

Payette River, 198. 

Peale, a. C, Three Forks Folio U. S. 
Geol. Surv., 317; U. S. Geol. and Geog. 
Siirv. of Col. and Adj. Terr., 383. 

Peat, 724. 

Pembina Mountains, 410. 

Pend Oreille Mountains, 302. 



Peneplain of the Prairie Plains, 

dissection of, 462; surface of, 462; 

regional illustrations of, 462. 
Penobscot River, 644. 
Peorian Interglaqal Stage, 466. 
Perry, J. H., Geology of Monadnock 

Mountain, 637. 
Petermann , , Mitteilungen , 551; 

Natur Wissenschaftliche Wochenschrift, 

Peter, R., Comparative Views of the 
Composition of the Soils, Limestones, 
Clays, Marls, etc., of the Several Geolog- 
ical Formations of Kentucky, 704. 

Peter's Mountain, 673. 

Phosphorus, as soil element, 72. 

Physiographic Regions, defined, 108; 
boundaries of, 108; similarities among 
features of, 109; dissimilarities among 
features of, 109; great size of, 109. 

Piedmont Plateau, soil of, 23; rocks in, 
587; feldspathic rock of, 597; elevation 
of, 612; origin of name of, 623; border 
features of, 624; landscape of, 624; 
even contour of, 624; cycles of erosion 
in, 625; deeply decomposed rock of, 
625; streams of, 625; rocks of, 625; 
relation of rocks to land forms of, 626; 
Triassic of the Atlantic Slope, 626; 
local development of Triassic rock in 
older Appalachians, Fig. 254, p. 627; 
characteristic features of, 629; prongs 
of, 630; four crystalline prongs of the 
older Appalachians, Fig. 257, p. 630; 
characteristic terminal-moraine topog- 
raphy, Fig_. 259, p. 633; soils of, 633; 
residual soils of, 634. 

Piedra River, 374. 

Pinal Range, 246. 

Pine Creek, 670. 

Pine Ridge, altitude of, 405. 

Pink Cliffs, 261, 265. 

Piper, C. V., Science, 534. 

PiRSsoN, L. v.. Rocks and Rock-making 
Minerals, 25, 37; Rocks and Rock 
Minerals, 63; Petrography and Geology 
of Igneous Rocks of Highwood Moun- 
tains, 449. 

Pisgah Range, direction of, 607; spruce 
forests of, 614. 

Pitt River, old valley of, 140. 

Plant x\ction, wedging force of roots, 
20; oxidation by, 20; root penetration 
in arid soils and subsoils, 32. 

Plant Forms, succession of, on rock, 21; 
on landslips, 21. 

Plants, distribution in Coalinga district, 
44; new species developed by chemical 
differences in soil, 62; relations of soil 
elements to, 65; selections of soil 
substances, 66; essential foods, relative 



INDEX 



751 



amounts in acre-foot, 73; total and 
available food, 73. 

Plummer and Gowsell, Fcrest Condi- 
tions in Lincoln Forest Reserve, 404. 

Plummer, F. G., Forest Conditions in 
Black Mesa Forest Reserve, Ariz., 287. 

PocoNO Mountain, 690. 

Porcupine Range, 569, 575. 

Pore Space, and tilth, 28; diagrams to 
illustrate, 28; extent of, 28; minimum 
and maximum of, 29. 

Potassium, as soil element, 71; in arid 
soils, 97. 

Po\\t)er River Range, 209. 

Powell, J. W., Lands of Arid Region of 
U. S., 43, 58, 259, 266, 287, 288; 
Geology of Uinta Mountains, 345, 346; 
Physiographic Regions of U. S., 477. 

Powell Plateau, 289. 

Prairie Plains, extent and characteris- 
tics of, 460; timber of, 460; dense agri- 
cultural population on, 460; general 
appearance of, 460; principal relief 
features of, 461; typical view of. Fig. 
174, p. 461; peneplain of, 462; north- 
south section, Fig. 175 p. 464; centers 
of glaciation of, 465; glacial and inter- 
glacial periods, 466; topographic effects 
of glaciation on, 469; drainage and 
soil effects of glaciation on, 469; ter- 
minal moraines and till sheets of, 470; 
distribution of glacial moraines and 
■direction of ice movement in southern 
Michigan, northern Ohio, and Indiana, 
Fig. 178, p. 471; glacial map of northern 
Illinois, Fig. 179, p. 472; drift cover in 
Michigan, 473; terminal moraines in 
eastern North Dakota, 473; lake plains 
of, 476; proglacial lakes, 477; soilsof the 
glaciated country in, 486 ; soil of old lake 
bottoms in, 486; loess deposits of, 488; 
tree growth of, 489; distribution of 
prairie and woodland in Illinois, Fig. 
190, p. 490; tree growth on prairies of 
Texas, 491; driftless area of, 494. 

Prairies of Texas, tree growth of, 491; 
Western Cross Timber of, 492; Eastern 
Cross Timber of, 492; Cross Timbers of. 
Fig. 191, p. 493. 

Preble, E. A., Biological Investigation of 
the Athahaska- Mackenzie Region, 41, 
570- 

Precipitation, in U. S., 117. 

Presidential Range, importance of in 
White Mountain district, 645; struc- 
ture of, 647. 

Priest River Mountains, in northern 
Rockies, 298; topography of, 304; 
altitudes in, 304; forest growth of, 304. 

Prieta Mesa, 283. 



Proglacial Lakes, origin of, 478 
history of, 481; Lake Duluth, Figs. 
186, 187, p. 482. 

Prospect Peak, Cal., relations ot 
former and present forest, Fig. 34, p- 

155- 
Provincetown, sand dunes of, 504. 
Public Land, vacant, location of. Fig. 

61, p. 230. 
Pueblo Range, 227. 
PuENTA Hills, 184. 
PuERCo River, 274. 
PuGET Sound, 177. 
Puget Sount) Valley, 178. 
PuMPELLY, Wolff, and Dale, Geology 

of Green Mountains in Massachusetts, 

639, 650. 
PuRCELL Range, in northern Rockies, 

298; subdivisions of, 306; trenches of, 

306; forests of, 306. 
PuRCELL Trench, 301. 
Purdue, A. H., Winslow Folio U. S. 

Geol. Surv., 453. 
Pyramid Canyon, 238. 

Rabbit Valley, 263. 

Rainfall, cause of, 117 ; place of heaviest, 
117; mean annual, Fig. 19, p- 118; 
annual, percentage of in six warmer 
months. Fig. 22, p. 120; at San Luis 
Obispo, 146. 

Raisin River, 483. 

Raleigh, location in fall line, 499. 

Randolph Range, trend of, 645. 

Ransome and Calkins, Geology and Ore 
Deposits of CcEur d'Alene District, 
Idaho, 302. 

Ransome, F. L., Mother Lode, District 
Folio U. S. Geol. Surv., 176; Great 
Valley of California, 180; Globe Folio 
U. S. Geol. Surv., 246; Geology of Globe 
Copper District, Arizona, 254; Geology 
and Ore Deposits of Coeur d'Alene Dis- 
trict, Idaho, 301; Report on Economic 
Geology of Silverton Quadrangle, 375. 

Raton Mesa, Fisher's Peak and, Fig. 
140, p. 394; basalt flows of, 396; tree 
growth of, 397. 

Reading Prong, 631. 

Red Bluff, Cal., 181. 

Red Desert, 338. 

Redlands and San Bernardino and 
San Gorgonio Peaks, California, 
Fig. 26, p. 136. 

Red River, headwaters of, 409; and 
drainage, 410; rafts of, 534; timber 
jam of Red River raft. Fig. 214, p. 
535; timber deadened in temporary 
raft lake. Fig. 216, p. 536; one of the 
rafts of, Fig. 217, p. 536; map showing 
diversion of. Fig. 218, p. 537; growth 



752 



INDEX 



and drainage of raft lakes, Fig. 219, 
P- 538. 
Red River Valley, drainage changes of, 
485; fertile soil of, 485; lakes of, in 
Louisiana, Fig. 215, p. 535. 
Red Valley, 442. 
Reed, C. A., 458. 

Reid, J. A , Geomorphogeny of Sierra 
Nevada Northeast of Lake Tahoe, 171. 

Remmel, height of, 157. 

Rensselaer Plateau, 681, 682. 

Rice and Gregory, Manual of Conn. 
Geologv, 660. 

Richard'son, G. B., E! Paso Folio U. S. 
GeJ. Surv., 393, 401, 402. 

Rich, J. L., Physiography of the Bishop 
Conglomerate, Southwestern Wyoming, 
342. 

Riding Mountains, 410. 

Rio Grande, and Arizona Highlands, 
246; basins of, 400; flood plain of, 401; 
great and sudden floods of, 401. 

Rio Grande Valley, basins of, 400; 
view of, Fig. 143, p. 400. 

Rivers of Great Basin, causes for 
variation in length of, 217; causes for 
variation in discharge of, 217. 

Riverwash, 725. 

Roan or Book Plateau, in Grand River 
district, 277; topography of, 278; 
vegetation of, 279. 

Robinson, , Am. Jour. Sci., vol. 

24, 272. 

Robinson, H. H., Tertiary Peneplain of 
Plateau District and Adjacent Country 
in Arizona and New Mexico, 256, 285; 
New Erosion Cycle in Grand Canyon 
District, Ariz., 284. 

Rock Outcrop, 724. 

Rock Types, analyses of in fresh and 
decomposed condition, 728. 

Rocky Mountains, northern Rockies, 
298-328; central Rockies, 329-355; 
southern Rockies, 356-386. 

Rocky Mountain System, decision of 
U. S. Geographic Board on, 298. 

Rocky Mountain Trench, unique char- 
acter of, 301. 

Rogue River, mountains, 139, 141, 177; 
valley, 143. 

Roosevelt, Theodore, The Winning of 
the West, 586, 695. 

Root Penetration, in arid soils and 
subsoils, 32. 

Rouge River, 483. 

Rough Stony Land, 724. 

Russell, L C, A Geological Reconnais- 
sance in Central Washington, 149; Pre- 
liminary Paper on Geology of Cascade 
Mountainsin Northern Washington, 150; 
North America, 148, 178, 212; 8th Ann. 



Rept. U. S. Geol. Surv., 167; Geology 
and Water Resources of Snake River 
Plains of Idaho, 192, 193, 194, 195, 200; 
Reconnaissance in Southeastern Wash- 
ington, 196, 205; Geology and'Water Re- 
sources of Central Oregon, 203; Notes on 
Geology of Southwestern Idaho and South- 
eastern Oregon, 207; Geological History of 
Lake Lahonton, 214, 225; ^th Ann. Rept. 
U. S. Geol. Surv., 214; Lakes of North 
America, 216; Mon. U. S. Geol. Surv., 
228; Timber Lines, 232, 233; Surface 
Geology of Portions of Menominee, Dick- 
inson, and Iron Counties, Mich., 468; 
Rept. Mich. State Geologist, 717. 

Sacramento Mountains, 387, 390, 402. 

Sacramento River, level of channel, 182. 

Sacramento Valley, and Pacific coast 
downfold, 177; geographic features, 
181; bordered by, 182, 183. 

Saddle Mountain, Oregon, 143. 

Saguenay River, canyon of, 561; and 
lowland strips, 683. 

Salem Platform, in Ozark region, 452. 

Salisbury, R. D., Physical Geography of 
New Jersey, 516, 633. 

Salmon Mountains, in Klamath Moun- 
tains, 139; trend of, 141. 

Salmon River, 323. 

Salmon River Canyon, view across, 
Fig. loi, p. 321. 

Salmon River Mountains, and Snake 
River Valley, 202; and Blue Mountains, 
207; in northern Rockies, 298. 

Salt-consuming Plants, of arid regions, 
100. 

Salt Lakes of the Great Basin, water 
of, 212; ephemeral character of, 212; 
playas of, 212; appearance and dis- 
appearance of, 212. 

Salton River, and Colorado River, 240. 

Salton Sink Region, geologic changes 
in, 241; recent changes in, 241; map of, 
Fig. 66, p. 242. 

San x\ndreas Range, 391. 

San Antonio, location in fall line, 499. 

San Bernardino Range, distinct topo- 
graphic unit, 136; Bear Valley and 
adjacent country. Fig. 27, p. 137; 
valley and mountain, 138; glacial fea- 
tures of, 138; and Pacific coast down- 
fold, 177; and valley of southern 
California, 184. 

Sant) Dunes, control of, 504; sand bind- 
ing methods, 505. 

Sanders Peak, 331. 

Sandhill, 725. 

Sandia Mountains, 389, 391. 

San Diego Mountains, 399. 

Sands Mountain, 666. 



INDEX 



753 



Sandstone Hills, origin of, 408. 

Sanford, S., 2d Ann. Kept. Fla. Geol. 
Surv., 546. 

San Francisco Mountains, and relief 
of Colorado Plateaus, 258; and San 
Francisco Plateau, 272, 273; junipers 
on, 287; study of, 291; timber zones on. 
Fig. 83, p. 293; topography of, 294; 
origin of, 294; water courses of, 294; 
soils of, 294; forests of, 295; and Mo- 
gollon Mesa, 296; volcanic, 292; height 
of, 294; origin of, 294; " tanks " of, 
294. 

San Francisco Plateau, topography of, 
272. 

San Gabriel Range, physiographic char- 
acter, 135; and Pacific coast downfold, 
177; and valley of southern California, 

" 184. 

Sangamon Interglacial Stage, 466. 

San Gorgonia Mountain, 138. 

Sangre de Cristo Range, extent and 
features of, 372; relation to San Luis 
Valley, 384; terminal moraines of, 384; 
and Arkansas River, 409. 

San Jacinto Mountains, precipitous 
sides of, 135; and valley of southern 
California, 184. 

San Joaquin River, 182. 

San Joaquin Valley, composition of 
alkaH salts in, 98; and Pacific coast 
downfold, 177. 

San Jose Mountains, tree growth, 249. 

San Juan Mountains, canyons of, 374; 
southwestern border of, 374; landslides 
of, 374; landslide surface below Red 
Mountain, near Silverton, Fig. 126, 
p. 375; rainfall of, 376; vegetation of, 
376- 

San Juan River, 274, 374. 

San Luis Mountains, tree growth, 249, 
250. 

San Luis Obispo, rainfall at, 146; soils 
of, 147; vegetation of, 147. 

San Luis Park, 383. 

San Luis Valley, cross section of, Fig. 
131, p. 383; north end of, Fig. 132, p. 
384; vegetation in, 386. 

San Mateo Mountains, volcanic mate- 
rial of, 390; north end of. Fig. 144, p. 
402; tree growth in, 402. 

San Miguel Mountains, 277. 

San Miguel River, 374. 

San Pedro Hill, 186. 

San Rafael Mountains, 177. 

San Rafael Swell, 273. 

Santa Ana Mountains, character of, 
13s; and valley of southern California 
184. 

Santa Ana Valley, 135. 

Santa Catalina Range, 246, 253. 



Santa Cruz Ranges, physiographic 

character of, 132. 
Santa Cruz River, forests of, 250. 
Santa Lucia Range, physiographic 

character, 132. 
Santa Margherita, river valley, 135. 
Santa Monica Mountains, 186. 
Saratoga Cuesta, 533. 
Sargent, C. S., Mamial of Trees of North 

America, 78, 233. 
Satas Ridge, landslides on, 222. 
Savory Plateau, 340. 
Sawatch Range, extent of former 

glacier systems in parts of Park and 

Sawatch ranges. Fig. 125, p. 371; 

glaciation of, 372; and Arkansas River, 

409. 
Sawtooth Mountains, 198, 324. 
ScHELL Creek Range, trees of, 235. 
ScHiMPER, , Plant Geography upon 

a Physiological Basis, 41, 62. 
Schloesing, Th., Constitution of the Clays, 

37- 
Schrader, F. C, Independence Folio 

U. S. Geol. Surv., 464. 
Schreiner and Reed, Role of •Oxidation 

in Soil Fertility, 21; Certain Organic 

Constituents of Soils in Relation to Soil 

Fertility, 76, 80, 84. 
Schreiner and Shorey, Isolation of 

Harjnful Organic Substances from Soil, 

76, 80, 81; Chemical Nature of Soil 

Organic Matter, 79, 87. 
ScHROON Lake, 583. 
ScHucHERT, Charles, Paleogeogrcphy of 

North America, 730. 
Scott, mountains, 139, 141; valley, 142. 
Selkirk System, 302. 
Selkirk Trench, 301. 
Seven Devils, 195, 196 ?o6. 
Second EroSjON Cycle, in Colorado 

Plateaus, 2S3; stripping in, 284; mature 

valleys of, 284. 
Second Mountain, 673. 
Semple, E. C; The Anglo-Saxons of the 

Kentucky Mountains, 695. 
Sevier Plateau, 262. 
Shaler and Woodworth, Geology of the 

Richmond Basin, 629. 
Shaler, N. S., The Origin and Nature of 

Soils, 4, 48, 706; Geology of the Cape 

Cod District, 502, 503; Report on Geology 

of Martha's Vineyard, 506; 10th Ann. 

Rept. U. S. Geol. Surv., 552; The Trans- 
portation Routes of Kentucky and Their 

Relation to the Economic Resources of 

the Commonwealth, 695. 
Sharburger, Noll, Schenck, and Kar- 

STEN, Textbook of Botany, 92. 
Sharp Mountain, 673. 



754 



INDEX 



Shaw, E. W., High Terraces and Aban- 
doned V alleys in Western Pennsylvania, 
689. 

Shawnee Hills, 451. 

Shawnee, Idaho, 198. 

Shaw's Park, 385. 

Sheep Mountain Table, 414. 

Shenandoah Valley, relation to Great 
Appalachian Valley, 665; breadth of, 
666. 

Shimek, B., Bull. Geol. Soc. Am., 466; 
Jour. Geol., 488. 

Shinarump Cliffs, 261. 

Shiwits Plateau, topography of, 2O9. 

Shonkin Sag, 413. 

Siebenthal, C. E., Geology and Water 
Resources of San Luis Valley, 373, 381, 
384, 385 386; Notes on Glacialion in 
Sangre de Cristo Range, 384. 

Sierra Blanca, 390, 393. 

Sierra de Santiago, 390. 

Sierra Guadalupe, 390. 

Sierra Madre of Mexico, 184. . 

Sierra Madre Range, Wyoming, 
smooth contours of, 342; structure of, 

343- 

Sierra Mogollon, 292. 

Sierra Nevada Mountains, extent of, 
166; geologic features of, 166; physi- 
ographic features of, 166; eastern 
border of, 167, 168; western slope of, 
168; canyons of, 170; categories of 
form, 171; drainage of, 171; northern 
end of, 172; soils c^, 172, 173; precipita- 
tion of, 173; forest belts of, 173, 176; 
relation of topography to rainfall. 
Fig. 41, p. 173; climate of, 173; zones 
of vegetation in, 173; forests of, com- 
pared with Coast Range vegetation, 
176; limitations in use of forests of, 
176; and Pacific coast downfold, 177; 
and Great Valley of California, 180; 
and water supply of Lake Tulare, 183. 

Silicon, as soil element, 67. 

Silt, described, 35; of Colorado River, 
238. 

Silvies River, forests and stream flow in 
basin of, 6. 

Siskiyou Mountains, 139, 141, 177. 

Skagit Mountains, terminating Cas- 
cades, 156; composition of, 157; physio- 
graphic features of, 158; western por- 
tion of. Fig. 36, p. 159; and Skagit 
River, 160; climatic conditions, 165. 

Skagit Valley, 165. 

Skeleton Mesa, 275. 

Slighter, C. S., Motions of Underground 
Waters, 29, 45, 48. 

Slide Mountain, 691. 

Slogan Mountains, 302. 

Slogan River, 302. 



Smith and Calkins, Geological Recon- 
naissance Across Cascade Range near 
4gth Parallel, 157, 158, 159, 160, 161, 
165, 202. 

Smith and Macauley, Mineral Re- 
sources of Alabama, 67. 

Smith ant) Willis, Physiography of the 
Cascades in Central Washington, 150, 
154, 155. 160. 

Smith, E. A., Under groiind Water Re- 
sources of Alabama, 521, 522. 

Smith, M., Gardening in Northern 
Alaska, 56; Raising Crops in Far 
North, 56; Agriculture and Grazing in 
Alaska, 56. 

Smoky Mountains, Idaho, 324. 

Smythe, H. L., Crystal Falls Iron-bearing 
District of Michigan, 574. - 

Snake Range, Nevada, east side of, 
Fig. 64, p. 234. 

Snake River, lavas, 192, 193; canyon of, 
at the Seven Devils, Fig. 50, p. 195; 
gorge, 195; canyon of, 196; elevation 
of plains of, 197; utilization of water 
of, 205. 

Snake River Valley, hydrographic 
changes in, 196; present extent of, 197; 
rainfall in, 202; and Lake Bonneville, 
214. 

Soap Lake, 201. 

Sodium, as soil element, 70. 

Soil, in relation to life, i; and forest, i; 
cover, 3; forces making, 7; erosion, 
amount of in U. S., 13; temperature 
effects on, 14; effects of wind on, 16; 
effects of bacteria in forming, 17; made 
by animals and higher plants, 19; plant 
action on, 20; diversity, 22; transported, 
24; physical features of, 27; particles, 
size, and weight of, 27; specific gravity 
of, 27; pore space in, 28; flocculation 
of, 29; and subsOil, 30; air in, t,^,; water 
supply of, 41; temperature, 55; rate 
of flow of heat through, 61; chemical 
features of, 62; relative value of chemi- 
cal quaHties of, 62; minerals, 63; ele- 
ments of, 64; fertility, determination 
of, 74; harmful organic constituents 
of, 76; humus and nitrogen supply of, 
77; organic matter in, 79; humus, 
amount and derivation of, 80; of arid 
regions, 95; salts of in arid regions, 95; 
action of carbonate of soda on, 100; 
classification, 102; analysis, purpose 
of, 104; bases of classifications, 105; 
scheme of classification of, 722; un- 
classified materials, 723; special desig- 
nations, 723. 

Soil Class, 721. 

Soil Series, 723. 



INDEX 



755 



Soil Survey in Forest Physiography, 
outline for, 726. 

Soil Temperature, ecologic relations, 
55; importance in plant growth, 56; 
influence of water on, 56; contrasts 
between sandy and clayey soils, 57; 
and chemical action, 57; influence of 
slope exposure, soil color, rainfall, and 
vegetation, 58; influence of surface 
slope on amount of heat received. 
Fig. 8, p. 58; variations with depth, 60. 

Soil Type, 723. 

Soil Types, distribution by regions, 25. 

Solution, ii. 

South Carolina-Georgia Section of 
Coastal Plain, wave and current- 
built sand reefs of, 519; vegetation of, 
520. 

Southern Appalachians, axes of de- 
formation of. Fig. 237, p. 593; physio- 
graphic map of, Fig. 238, p. 595; curve 
illustrating relation of topographic 
relief to lithologic composition in, 
Fig. 239, p. 598; height of, 603; topo- 
graphic qualities of, 604; drainage 
features of, 604; contrast of to sur- 
rounding tracts, 604; Pisgah Moun- 
tains from Eagles Nest near Waynes- 
ville, Fig. 242, p. 605; cooler climate of, 
605; rainfall of, 606; dryness of south- 
east slopes of, 606; physiographic de- 
velopment of, 607; geologic structure 
of a region of. Fig. 243, p. 607; struc- 
tural irregularities in, 607; smoothest 
contours in, 607; Roan Mountain, 
Tenn., Fig. 244, p. 608; adjustments 
to structure in, 608; local peneplain of 
at Asheville, 609; local plateaus in, 
609; basins of, 610; gorges of, 610; 
cover of, 610; Asheville basin in. Fig. 
245, p. 611; mountaineers of, 611; soils 
of, 612; distribution of forests and 
cleared land in. Fig. 246, p. 613; grassy 
" bald " and spruce border. White 
Top Mountain, Fig. 247, p. 613; 
vegetation of, 614; distribution of 
timber of, 614; higher coves of, 614; 
cultural and forestry methods in, 615; 
erosion in, 615; total area still forested, 
615; porous soils of, 615; allowable 
limit of steepness for cleared lands in, 
615; evil effects of deforestation in, 
616; forest physiography of, 616; 
relation of primeval forests of to 
slopes and soils, 616; protection 
against erosion of by parallel ditches. 
Fig. 248, p. 617; erosion of checked by 
covering gulleys with brush, Fig. 249, 
p. 617; erosion of checked by brush 
dams. Fig. 250, p. 618. 

Southern California, beach lands. 



coastal plains, and mountains of, 
Fig. 44, p. 185; inner edge of coastal 
plain of. Fig. 45, p. i86; forests and 
water supply, 186; fault-block moun- 
tains in, 222. 

Southern California, Valley of, 
location and cHmatic features, 184; 
topography and drainage, 184; soils 
of, 190. 

Southern Cascades, older forests of, 
156; younger forests of, 156; height of, 
156; rainfall of, 156. 

Southern District of Superior High- 
lands, development of in central 
northern Wisconsin, 577; character 
and relations of pre-Cambrian and 
cretaceous peneplains in northern Wis- 
consin, Fig. 233, p. 577. 

Southern Oregon Lakes, size of, 214; 
changes in outline of, 214. 

Southern Plateau District, 273. 

Southern Rockies, location map of. 
Fig. 117, p. 356; main topographic 
features of, 357; principal subdivisions 
ofj 357) generalized east-west section 
near boulder. Fig. 118, p. 357; eastern 
foothills of, 357; igneous border of, 
360; foothill terraces of, 362; longitud- 
inal profiles of five prominent ranges 
in Rocky Mountain province. Fig. 121, 
p. 363; section on common border of 
Great Plains and southern Rockies, 
Fig. 122, p. 364; topographic profile 
and distribution of precipitation across 
the Wasatch Mountains and the 
southern Rockies, Fig. 124, p. 369; 
western border ranges of, 373; parks 
of, 3S1. 

Southern Wyoming, basin plains of, 
and minor ranges on them, 338; hog- 
back topography of inclined beds, 
Fig. 109, p. 341; mountains of the 
Encampment district, Fig. no, p. 

343- 
South Fork Range, 140, 141. 
South Park, 383. 
South Table Mount.ain, 361. 
Spalding, V. M., Distribution and Move- 
ments of Desert Plants, 3. 
Spanish Peaks, bordering platform of, 

360; timber growth of , 361. 
Spanish Wasatch, canyons of, 227; 

ravines, spurs, and terminal facets of, 

Fig. 60, p. 227. 
Specific Gravity, of soil, 27. 
Spencer, J. W., Deformation of Algonkian 
Beach and Birth of Lake Huron, 483. 
Spenser, A. C, Copper Deposits of 

Encampment District, Wyoming, 343; 

Prof. Paper U. S. Geol. Surv., No. 26, 

367- 



756 



INDEX 



Spillman, W. J., Renovation of Worn^ 

out Soils, 78; Science, 534. 
Springfield Lake, 643. 
Springfield Plain, inclination of, 452. 
Spruce Forest of Canada, location, 

characteristic trees, physical relations, 

123. 
Spurr and Garey, Geology of Georgetown 

Quadrangle, 365, 366, 368, 369. 
Spurr, J. E., Descriptive Geology of 

Nevada South of 40th Parallel, 167, 233. 
Squaw Creek, canyon of, 172. 
Staten Island, former condition of, 502. 
St. Croix Basin, 644. 
Stearns, R. E. C, Remarks on Fossil 

Shells from the Colorado Desert, 241. 
Stehekin-Chelan River, 161. 
Steilacoom Plains, Tacoma, vegeta- 
tion of, 43, 62. 
Stein Mountains, Oregon, 207. 
Stevens, J. C, Water Power of the Cas- 
cade Range, 5, 7, 147. 
Stevenson, J. J., Geology of a Portion of 

Colorado, 373. 
Stillwater River, 332. 
St. John, Orestes, U. S. Geol. and Geog. 

Surv., of Terr., 332, 344, 345. 
St. Lawrence Valley, 558, 683 
St. Mary's River, 414. 
Stone Harbor, sand dunes of, 504. 
Stone Mountain, Georgia, form of, 16. 
Stone Mountain, MifHin Co., 677. 
Stony Mountain, 673. 
Stose, G. W., Mercersburg-Chambers- 

burg Folio U. S. Geol. Stirv., 672. 
Strawberry Range, 208, 209. 
Sub-Aftonian, or Nebeaskan Glacial 

Stage, 466. 
Subsidence Method, of soil analysis, 103. 
Subsoil, and soil, 30; root penetration in, 

32; regulating action of on water of 

surface soil, 52; relation of to water 

content of surface soil, 52. 
Sulphur, as soil element, 72. 
Sulphur Cuesta, 533. 
Summer Lake Valley, 225. 
Sun Dance Hills, 445. 
Superior Highlands, relation to Lauren- 

tian Plateau, 555; typical drainage 

irregularities in, Fig. 229, p. 572; 

glacial features of, 572; boundaries of, 

Fig. 330, p. 573; "muskeg" of, 573; 

representative districts of, 574-578; 

deformation of strata near Porcupine 

Mountain, Mich., Fig. 231, p. 575; 

structure and topography of southern 

border of, Fig. 232, p. 576. 
Surface Tension, 51. 
Suzuki, ., Bull. Col. Agri., Tokio, 

84. 
Swamp, 725. 



Swamp Lands of the United States, 

Fig. 221, p. 549. 
Sweet Grass Hills, 413. 

Taconic Range, 681. 

Taff, J. A., Report on Geology of Ar- 
buckle and Wichita Mountains, 456, 
459; Structural Features of Ouachita 
Mountain Range, 457; Coalgate Folio 
U. S. Geol. Surv., 464. 

Tahoe Lake, 167, 171, 172, 212. 

Tallulah Falls, 610. 

Tallulah River, gorge of, 610. 

Talus Slopes, vegetation of, 22. 

Tampa Bay, 553. 

Tanner's Crossing, 276. 

Tarr, R. S., Physical Geography of New 
York Slate, 580; Watkins. Glen-Cata- 
tonk Folio U. S. Geol. Surv., 693, 694; 
Decline of Farming in Southern-Central 
New York, 707; Watkins Glen and Other 
Gorges of the Finger Lake Region of 
Central New York, 710, 711; Drainage 
Features of Central New York, 711. 

Temperature Effects, on rock masses, 
Fig. I, p. 14. 

Temperature, variation of with depth 
of soil, 15, 60; zones of western hemi- 
sphere. Fig. 14, p. 113; extremes of, 
114; maximum temperatures in the 
U. S., 115; of mountain summits, 115; 
normal,for July, Fig. 15, p. 114; normal, 
for January, Fig. 16, p. 115; mean 
annual range of, 117; daily range of in 
U. S., 117; absolute minimum. Fig. 20, 
p. 119. 

Tennessee River, course of, 668. 

Tennessee Valley, relation to Great 
Appalachian Valley, 665. 

Terry Peak, 445. 

Teton Mountains, situation in Rocky 
Mountains, 329; peaks and passes in, 
343; canyons of, 344; forest cover of, 

344- 
Texas, physiographic subdivisions of, 
Fig. 150, p. 417; tree growth on prairies 
of, 491; cross timbers of, Fig. 191, p. 

493- 

Thompson, A. H., in Powell's Lands of 
Arid Region, 287. 

Thousand Islands, and preglacial drain- 
age, 476. 

Tight, W. G., Am. Geol., 398; Drainage 
Modifications in Southeastern Ohio and 
Adjacent Parts of West Virginia and 
Kentucky, 600. 

Todd, J. E., Aberdeen-Redjield Folio U. S. 
Geol. Surv., 474. 

ToLMAN, C. F., Erosion and Deposition 
in Arizona Bolson Region, 237. 

ToROWE.AP Valley, 270. 



INDEX 



757 



TouMEY, J. W., Relation of Forests to 
Stream Flow, i88; La Ventana, Appa- 
lachia, 253. 

Tower, W. S., The Mississippi River 
Problem, 526; Regional and Economic 
Geography of Pennsylvania, 631, 632, 
671, 673, 677, 678, 687, 690. 

Trail Ridge, 545. 

Transition Province, characteristics 
of, 122. 

Trans-Pecos Highlands, relation to 
Arizona Highlands, 246; mountains 
and basins of, 387; fault-block origin 
of, 387; mountain types in, 389; east- 
west section across, Fig. 135, p. 390; 
fault-block mountain in. Fig. 136, p. 
391; volcanic mountains and plateaus 
of, 393; drainage features in, 397; 
longitudinal basins in, 398; climate of, 
401; soils of, 402; vegetation of, 402; 
tree growth in, 403; grasses of, 404; 
range of timber species in. Fig. 145B, 
p. 404. 

Trans-Pecos Province, mountain ranges 
of. Fig. 133, p. 388. 

Transported Soil, 24. 

Trenches, longitudinal, of second rank 
302. i 

Trenton Prong, 632. 

Triassic Rocks, distribution of, 626; 
local development of, Fig. 254, p. 627; 
structure of, 628; relations of igneous 
rocks to sedimentary strata in New 
Jersey, Fig. 255, p. 628; palisades of 
the Hudson from the Jersey side, 
Fig. 256, p. 62; topographic expression 
of, 629. 

Trinity, mountains, 139, 141; valley, 142. 

Truckee River, and Lake Tahoc, 171; 
run-off, 216. 

Truxton Plateau, 254. 

Tuba City, 283. 

Tulare Lake, situation, 182; basin of, 
183; changes recent years, 183. 

Tulare Valley, situation, 183. 

TuLAROSA Desert, 399. 

Tule (Scirpus lacustris), 181. 

TuNiCHAi Mountains, 275. 

Tuolumne River, 170. 

Turner and Ransome, Big Trees Folio 
U. S. Geol. Surv., 175; Sonora Folio 
U. S. Geol. Surv., 190. 

Turner, H. W., 14^^ Ann. Rept. U. S. 
Geol. Surv., 166, 167. 

Turtle Mountain, 411. 

TusAYAN, Ariz., 276. 

Tuscaloosa, location in fall line, 499. 

TuscARORA Explorations, 128. 

TuscARORA Valley, dimensions of, 677. 

TusHAR Plateau, location in High 
Plateaus, 262; relation to Markagunt 



Plateau, 264; topography of, 265; 

timber hne of, 265. 
Twelve Mile Park, 385. 
Tybee Island, sand dunes of, 504. 
Tyrrell, J. B., Genesis of Lake Agassiz, 

465- 

Udden, J. A., Geological Romance, 17. 

UiNKARET Mountains, 270. 

Uinkaret Plateau, topography of, 269; 
vegetation of, 270; relation to others 
of the district, 270. 

Uinta Mountains, topographic outlines 
of, 345; structure of, 345; canyons of, 
346; stereogram and cross section of 
arch of. Fig. in, p. 346; forms due to 
glaciation, 347; glacier systems of, in 
the Pleistocene, Fig. 112, p. 348; forest 
growth in, 349. 

Umpqua River Valley, 143. 

Unaka Mountains, compared with 
Green Mountains, 588; direction 01, 
607; heights of, 608; elevation of, 612; 
relation to Newer Appalachians prov- 
ince, 665. 

Unaka Springs, Tenn., 610. 

Uncompahgre Plateau, in Grand River 
district, 277; topography of, 279; 
vegetation of, 280. 

Ungava Peninsula, 556. 

Upham, W., Tertiary and Early Quater- 
nary Base-leveling in Minnesota, Mani- 
toba, and Northwestward, 410, 411. 

Upper Austral Province, character- 
istics of, 123. 

Utah Lake, water of, 212. 

Ute Mountains, view from Cortez, 
Fig. 70, p. 257; height of, 258. 

Valles Mountains, 390. 

Van Hise and Leith, Adirondack Moun- 
tains, 583. 

Van Hise, C. R., Treatise on Metamor- 
phism, 9, 10, II, 73; Iron Ore Deposits 
of Lake Superior Region, 574. 

Van Winkle and Eaton, Quality of the 
Surface Waters of California, 145, 180, 
188. 

Vaughan, T. W., Sketch of the Geologic 
History of the Floridian Plateau, 545. 

Veatch, a. C, Underground Water 
Resources of Long Island, 46; Geog. and 
Geol. of Portion of Southwestern Wyo- 
ming, 342; Geology and Underground 
Water Resources of Northern Louisi- 
ana and Southern Arkansas, 501, 532, 
534- 

Vegetal Covering, types of, in relation 
to run-off, 4. 

Vegetation, effect of lime upon, 69; 
desert, typical view of, Fig. 63, p. 232; 



758 



INDEX 



zonal distribution of, in Arizona High- 
lands, 247. 

Ventura County, Cal., sand dunes of, 
504- 

Vermilion Bayou, character of, 529. 

Vermilion Cliffs, 261. 

Verrill, a. E., Occurrence of Fossilifer- 
ous Tertiary Rocks on the Grand Bank 
and Georges Bank, 502. 

Virginia-North Carolina Section of 
Coastal Plain, cypress trees of the 
Dismal Swamp, Fig. 206, p. 518; Albe- 
marle and Pamlico sounds. Fig. 207, 
p. 519; Chesapeake, Delaware, and 
tributary bays. Fig. 208, p. 519. 

Virgin River, mesas near, 261. 

Virgin Soils, plant food of, 75. 

ViviANiTE, and phosphoric acid, 72. 

Volcanoes of Colorado Plateaus, 
vegetation of, 293. 

VON Mohl, C, iJber das Erfrieren der 
Zweigspitzen mancher gewisser Phyco- 
chroniaceon, 55. 

VON Sachs, J., Handbuch der Experi- 
mental-Physiologie der Pjlanzen, 54; tlber 
den Einfluss der chemischen und der 
physikalischen Bcschajfenheit des Bo- 
dens auf die Transpiration, 65. 

VON TiLLO, A., 25. 

Waldemar and Lindgren, Clifton Folio 

U. S. Geol. Surv., 251. 
Walden Ridge, 666, 695. 
Walkill Valley, 681. 
Walloomsac Valley, 682. 
Ward, R. DeC, Climate, 112. 
Waring, G. A., Geology and Water 

Resources of a Portion of South-central 

Oregon, 216, 224, 225. 
Warington, R., Lectures on Some of the 

Physical Properties of the Soil, 47. 
Warming, E., (Ecology of Plants, 21, 22, 

34, 41, 42, 65, 66, 69, 70, 78, 79, 85, 93, 

105. 
Warren Peaks, 445. 
Wasatch Mountains, topography of, 

265; vegetation of, 265; former glacier 

systems of, Fig. 73, p. 266; main crest 

of, 267; Pleistocene glaciers of, 267. 
Wasatch Plateau, location in High 

Plateaus, 262. 
Washington, forests of, 162, 163. 
Washoe Lake, 171. 
Watatic Mountain, 637. 
Water, as aid to chemical action, 11; as 

a carrier, 12; and ice, mechanical action 

of, 12; supply of in soils, 41; relation 

to plant growth and distribution, 41; 

amount required by growing plant, 42; 

ground, in relation to surface and bed 

rock, Fig. 5, p. 44; table, contour map 



of, 45; table, surface of, 46; capillary, 
50; hygroscopic, 54; specific heat of, 56. 

Watersheds of United States, soil ero- 
sion on, 13. 

Weber Canyon, 227. 

Weed and Pirsson, Geology of the Little 
Rocky Mountains, 412, 451. 

Weed, W. H., Glaciation of Yellowstone 
Valley North of the Park, 335; Geology 
of Little Belt Mountains, 446, 448. 

Weidman, S., Geology of North-Central 
Wisconsin, 496, 577. 

Weiser, Idaho, 198. 

West Branch, 670. 

Western Forests and Woodlands, 
Fig. 29, p. 146. 

West Palm Beach, 547. 

West Spanish Peak, 360; Fig. 120, p. 
360. 

Wet Mountain Range, 408. 

White Cliffs, 261. 

White Hills, 411. 

White Mountain Notch, 647. 

White Mountains, Nevada, 168. 

White Mountains, N. H., rainfall of, 
121; dry timber line of, 232; effect of 
deforestation in, 619; exception to 
plateau feafiure of the province, 636; 
and bordering uplands, 645; heights of, 
645; Presidential Range of, 645; com- 
pared with Green Mountains, 646; 
geology of, 646; physiographic de- 
velopment of, 647; details of slopes in, 
647; former local glaciers on, 648; 
contrasted with Green Mountains in 
cultivation, 652. 

White River Plateau, topography of, 
277; country north of, 278. 

White River, source of, 277; relation to 
Grand River, 278. 

White River Table, 414. 

Whitney, J. D., Plain, Prairie, and 
Forest, 428. 

Whitney, Milton, Bull. U. S. Weath. 
Bur., 27; Soils in the Vicinity of Bruns- 
wick, Georgia, 520; Soils in the Vicinity 
of Savannah, Georgia, 520; Soils of 
Pender County, North Carolina, 520. 

Whittlesey and Warren, Great Ice 
Dams of Lakes Maumee, 477. 

WiCHiT.\ Mountains, border topography 
of, Fig. 173, p. 458; peaks of, 459. 

Wiley, H. W., Principles and Practice of 
Agric. Analysis: Soils, 19, 27, 37, 77, 
83, 86, 87. 

Willamette Valley, climate of, ii8;- 
narrowness of, 143; and Pacific coast 
downfold, 177, 178. 

Williams, Tarr and Kindle, Watkins- 
Glen-Catatonk Folio U. S. Geol. Surv., 
709. 



INDEX 



759 



Willis and Smith, Tacoma Folio U. S. 
Geol. Surv., 44, 142, 178, 191. 

Willis, Bailey, Slratigraphy and Struc- 
ture, Lewis and Livi^igston Ranges, 307, 
315; The Northern Appalachians, 591, 
670. 

Wilson, A. W. G., The Laiirentian Pene- 
plain, S55, 556, 564- 

Wilson, J., Modern Alchemist, 43. 

Wlnchell, N. H., sth Ann. Rept. Geol. 
and Nat. Hist. Surv. of Minn., 496. 

Wind, as agent in soil formation, 16; 
action of on humus, 78. 

Wlndham High Peak, 691. 

Wind River Mountains, situation in 
Rocky Mountains, 329; structure and 
topography of, 332; tree growth of, 
332- 

Winter River Valley, 225. 

Wisconsin Ice Sheets, importance of, 
468; four drift sheets, Fig. 177, p. 470; 



position of about Driftless Area, 
Fig. 180, p. 473. 

Yadkin River, 619. 

Yallo Bally Mountains, 141. 

Y'ampai Cliffs, 253. 

Yampa River, source of, 277. 

Yarmouth or Buchanan Interglacial 

Stage, 466. 
Yellowstone Valley, alkali soil of, 100. 
Y^osEMiTE Valley, typical portion of, 

Fig. 40, p. 169; canyon of, 170. 
Yuba River, level of, 182. 
Yuma, 240. 

Zilh-le-jini Mesa, 275, 276. 

Zone of Weathering, ii. 

ZoN, R., Loblolly Pine in Eastern Texas, 

5°, 53 1: 
ZuNi Plateau, topography of, 273; 

section of. Fig. 77, p. 274; forests of, 

287; and Mount Taylor, 296. 



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